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	$86.80	11.727%	$96.979	$96.98	$97.00	$97.00
Purchase #2	$79.79	8.874%	$86.8706	$86.87	$86.85	$86.90
Purchase #3	$149.88	12.562%	$168.7079	$168.71	$168.70	$168.70
Purchase #4	$61.74	13.563%	$70.1138	$70.11	$70.10	$70.10
Purchase #5	$133.38	8.328%	$144.4879	$144.49	$144.50	$144.50
Purchase #6	$57.50	6.634%	$61.3146	$61.31	$61.30	$61.30
Purchase #7	$76.52	8.379%	$82.9316	$82.93	$82.95	$82.90
7 purchase totals =	$645.61		$711.4054	$711.40	$711.40	$711.40