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	$201.91	10.628%	$223.369	$223.37	$223.35	$223.40
Purchase #2	$200.97	12.120%	$225.3276	$225.33	$225.35	$225.30
Purchase #3	$89.31	7.782%	$96.2601	$96.26	$96.25	$96.30
Purchase #4	$71.37	11.213%	$79.3727	$79.37	$79.35	$79.40
Purchase #5	$105.46	13.344%	$119.5326	$119.53	$119.55	$119.50
Purchase #6	$110.41	3.206%	$113.9497	$113.95	$113.95	$113.90
Purchase #7	$100.49	10.571%	$111.1128	$111.11	$111.10	$111.10
7 purchase totals =	$879.92		$968.9245	$968.92	$968.90	$968.90