Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$176.48	12.623%	$198.7571	$198.76	$198.75	$198.80
Purchase #2	$227.36	11.807%	$254.2044	$254.20	$254.20	$254.20
Purchase #3	$246.48	12.226%	$276.6146	$276.61	$276.60	$276.60
Purchase #4	$248.42	10.748%	$275.1202	$275.12	$275.10	$275.10
Purchase #5	$105.43	10.782%	$116.7975	$116.80	$116.80	$116.80
Purchase #6	$108.71	13.796%	$123.7076	$123.71	$123.70	$123.70
Purchase #7	$140.45	11.238%	$156.2338	$156.23	$156.25	$156.20
7 purchase totals =	$1,253.33		$1,401.4352	$1,401.43	$1,401.40	$1,401.40