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	$40.82	13.180%	$46.2001	$46.20	$46.20	$46.20
Purchase #2	$110.31	3.765%	$114.4632	$114.46	$114.45	$114.50
Purchase #3	$206.27	10.414%	$227.751	$227.75	$227.75	$227.80
Purchase #4	$63.52	3.490%	$65.7368	$65.74	$65.75	$65.70
Purchase #5	$18.93	6.403%	$20.1421	$20.14	$20.15	$20.10
Purchase #6	$13.31	4.620%	$13.9249	$13.92	$13.90	$13.90
Purchase #7	$216.33	12.439%	$243.2393	$243.24	$243.25	$243.20
7 purchase totals =	$669.49		$731.4574	$731.45	$731.45	$731.40