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	$189.75	3.489%	$196.3704	$196.37	$196.35	$196.40
Purchase #2	$165.62	9.798%	$181.8474	$181.85	$181.85	$181.80
Purchase #3	$58.37	13.267%	$66.1139	$66.11	$66.10	$66.10
Purchase #4	$55.47	7.755%	$59.7717	$59.77	$59.75	$59.80
Purchase #5	$41.39	6.361%	$44.0228	$44.02	$44.00	$44.00
Purchase #6	$146.56	9.162%	$159.9878	$159.99	$160.00	$160.00
Purchase #7	$34.35	11.573%	$38.3253	$38.33	$38.35	$38.30
7 purchase totals =	$691.51		$746.4393	$746.44	$746.40	$746.40