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	$198.57	13.673%	$225.7205	$225.72	$225.70	$225.70
Purchase #2	$39.97	6.164%	$42.4338	$42.43	$42.45	$42.40
Purchase #3	$101.46	13.353%	$115.008	$115.01	$115.00	$115.00
Purchase #4	$156.72	11.539%	$174.8039	$174.80	$174.80	$174.80
Purchase #5	$94.81	10.475%	$104.7413	$104.74	$104.75	$104.70
Purchase #6	$214.87	10.485%	$237.3991	$237.40	$237.40	$237.40
Purchase #7	$178.39	12.186%	$200.1286	$200.13	$200.15	$200.10
7 purchase totals =	$984.79		$1,100.2352	$1,100.23	$1,100.25	$1,100.10