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	$38.91	12.634%	$43.8259	$43.83	$43.85	$43.80
Purchase #2	$40.70	4.863%	$42.6792	$42.68	$42.70	$42.70
Purchase #3	$75.50	4.206%	$78.6755	$78.68	$78.70	$78.70
Purchase #4	$247.81	6.334%	$263.5063	$263.51	$263.50	$263.50
Purchase #5	$236.69	9.792%	$259.8667	$259.87	$259.85	$259.90
Purchase #6	$134.80	7.482%	$144.8857	$144.89	$144.90	$144.90
Purchase #7	$250.62	9.803%	$275.1883	$275.19	$275.20	$275.20
7 purchase totals =	$1,025.03		$1,108.6276	$1,108.65	$1,108.70	$1,108.70