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	$37.96	10.474%	$41.9359	$41.94	$41.95	$41.90
Purchase #2	$147.56	5.823%	$156.1524	$156.15	$156.15	$156.20
Purchase #3	$196.51	7.518%	$211.2836	$211.28	$211.30	$211.30
Purchase #4	$206.45	9.309%	$225.6684	$225.67	$225.65	$225.70
Purchase #5	$131.34	8.443%	$142.429	$142.43	$142.45	$142.40
Purchase #6	$86.72	8.140%	$93.779	$93.78	$93.80	$93.80
Purchase #7	$88.98	3.548%	$92.137	$92.14	$92.15	$92.10
7 purchase totals =	$895.52		$963.3853	$963.39	$963.45	$963.40