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	$208.73	12.825%	$235.4996	$235.50	$235.50	$235.50
Purchase #2	$224.67	10.256%	$247.7122	$247.71	$247.70	$247.70
Purchase #3	$132.62	6.565%	$141.3265	$141.33	$141.35	$141.30
Purchase #4	$81.94	13.853%	$93.2911	$93.29	$93.30	$93.30
Purchase #5	$233.40	6.140%	$247.7308	$247.73	$247.75	$247.70
Purchase #6	$89.31	10.190%	$98.4107	$98.41	$98.40	$98.40
Purchase #7	$89.92	12.129%	$100.8264	$100.83	$100.85	$100.80
7 purchase totals =	$1,060.59		$1,164.7973	$1,164.80	$1,164.85	$1,164.70