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	$228.83	6.132%	$242.8619	$242.86	$242.85	$242.90
Purchase #2	$42.77	9.681%	$46.9106	$46.91	$46.90	$46.90
Purchase #3	$233.85	3.260%	$241.4735	$241.47	$241.45	$241.50
Purchase #4	$93.59	12.340%	$105.139	$105.14	$105.15	$105.10
Purchase #5	$37.80	10.505%	$41.7709	$41.77	$41.75	$41.80
Purchase #6	$109.66	11.562%	$122.3389	$122.34	$122.35	$122.30
Purchase #7	$223.27	6.434%	$237.6352	$237.64	$237.65	$237.60
7 purchase totals =	$969.77		$1,038.1300	$1,038.13	$1,038.10	$1,038.10