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	$203.67	8.328%	$220.6316	$220.63	$220.65	$220.60
Purchase #2	$82.96	11.428%	$92.4407	$92.44	$92.45	$92.40
Purchase #3	$128.70	3.265%	$132.9021	$132.90	$132.90	$132.90
Purchase #4	$145.34	3.598%	$150.5693	$150.57	$150.55	$150.60
Purchase #5	$10.58	10.162%	$11.6551	$11.66	$11.65	$11.70
Purchase #6	$136.84	4.418%	$142.8856	$142.89	$142.90	$142.90
Purchase #7	$227.45	10.402%	$251.1093	$251.11	$251.10	$251.10
7 purchase totals =	$935.54		$1,002.1937	$1,002.20	$1,002.20	$1,002.20