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	$223.95	4.298%	$233.5754	$233.58	$233.60	$233.60
Purchase #2	$191.56	6.370%	$203.7624	$203.76	$203.75	$203.80
Purchase #3	$33.59	4.634%	$35.1466	$35.15	$35.15	$35.10
Purchase #4	$182.85	8.755%	$198.8585	$198.86	$198.85	$198.90
Purchase #5	$225.77	13.665%	$256.6215	$256.62	$256.60	$256.60
Purchase #6	$63.59	12.111%	$71.2914	$71.29	$71.30	$71.30
Purchase #7	$6.32	8.318%	$6.8457	$6.85	$6.85	$6.80
7 purchase totals =	$927.63		$1,006.1015	$1,006.11	$1,006.10	$1,006.10