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	$214.69	3.491%	$222.1848	$222.18	$222.20	$222.20
Purchase #2	$105.83	5.401%	$111.5459	$111.55	$111.55	$111.50
Purchase #3	$42.35	5.155%	$44.5331	$44.53	$44.55	$44.50
Purchase #4	$236.34	10.165%	$260.364	$260.36	$260.35	$260.40
Purchase #5	$48.56	11.699%	$54.241	$54.24	$54.25	$54.20
Purchase #6	$86.76	8.234%	$93.9038	$93.90	$93.90	$93.90
Purchase #7	$107.84	3.804%	$111.9422	$111.94	$111.95	$111.90
7 purchase totals =	$842.37		$898.7148	$898.70	$898.75	$898.60