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	$230.84	11.117%	$256.5025	$256.50	$256.50	$256.50
Purchase #2	$61.73	7.431%	$66.3172	$66.32	$66.30	$66.30
Purchase #3	$141.58	5.833%	$149.8384	$149.84	$149.85	$149.80
Purchase #4	$60.31	3.391%	$62.3551	$62.36	$62.35	$62.40
Purchase #5	$164.90	4.221%	$171.8604	$171.86	$171.85	$171.90
Purchase #6	$215.55	3.344%	$222.758	$222.76	$222.75	$222.80
Purchase #7	$201.95	7.823%	$217.7485	$217.75	$217.75	$217.70
7 purchase totals =	$1,076.86		$1,147.3801	$1,147.39	$1,147.35	$1,147.40