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	$79.89	8.275%	$86.5009	$86.50	$86.50	$86.50
Purchase #2	$59.86	4.777%	$62.7195	$62.72	$62.70	$62.70
Purchase #3	$89.94	3.139%	$92.7632	$92.76	$92.75	$92.80
Purchase #4	$233.38	10.267%	$257.3411	$257.34	$257.35	$257.30
Purchase #5	$58.54	10.474%	$64.6715	$64.67	$64.65	$64.70
Purchase #6	$192.50	10.438%	$212.5932	$212.59	$212.60	$212.60
Purchase #7	$236.66	10.254%	$260.9271	$260.93	$260.95	$260.90
7 purchase totals =	$950.77		$1,037.5165	$1,037.51	$1,037.50	$1,037.50