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	$236.55	10.556%	$261.5202	$261.52	$261.50	$261.50
Purchase #2	$141.76	12.816%	$159.928	$159.93	$159.95	$159.90
Purchase #3	$85.78	4.626%	$89.7482	$89.75	$89.75	$89.70
Purchase #4	$218.73	13.713%	$248.7244	$248.72	$248.70	$248.70
Purchase #5	$219.43	12.740%	$247.3854	$247.39	$247.40	$247.40
Purchase #6	$210.41	5.825%	$222.6664	$222.67	$222.65	$222.70
Purchase #7	$237.66	7.459%	$255.3871	$255.39	$255.40	$255.40
7 purchase totals =	$1,350.32		$1,485.3597	$1,485.37	$1,485.35	$1,485.30