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	$87.47	7.637%	$94.1501	$94.15	$94.15	$94.20
Purchase #2	$93.83	4.616%	$98.1612	$98.16	$98.15	$98.20
Purchase #3	$194.98	12.799%	$219.9355	$219.94	$219.95	$219.90
Purchase #4	$141.43	13.699%	$160.8045	$160.80	$160.80	$160.80
Purchase #5	$191.85	11.671%	$214.2408	$214.24	$214.25	$214.20
Purchase #6	$106.63	4.211%	$111.1202	$111.12	$111.10	$111.10
Purchase #7	$42.59	13.620%	$48.3908	$48.39	$48.40	$48.40
7 purchase totals =	$858.78		$946.8031	$946.80	$946.80	$946.80