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	$82.39	5.143%	$86.6273	$86.63	$86.65	$86.60
Purchase #2	$55.57	6.772%	$59.3332	$59.33	$59.35	$59.30
Purchase #3	$185.92	3.248%	$191.9587	$191.96	$191.95	$192.00
Purchase #4	$123.61	4.306%	$128.9326	$128.93	$128.95	$128.90
Purchase #5	$173.58	10.207%	$191.2973	$191.30	$191.30	$191.30
Purchase #6	$247.84	3.203%	$255.7783	$255.78	$255.80	$255.80
Purchase #7	$121.72	9.115%	$132.8148	$132.81	$132.80	$132.80
7 purchase totals =	$990.63		$1,046.7422	$1,046.74	$1,046.80	$1,046.70