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	$133.63	10.806%	$148.0701	$148.07	$148.05	$148.10
Purchase #2	$48.87	10.260%	$53.8841	$53.88	$53.90	$53.90
Purchase #3	$55.70	3.261%	$57.5164	$57.52	$57.50	$57.50
Purchase #4	$200.33	9.152%	$218.6642	$218.66	$218.65	$218.70
Purchase #5	$236.39	13.169%	$267.5202	$267.52	$267.50	$267.50
Purchase #6	$115.56	8.455%	$125.3306	$125.33	$125.35	$125.30
Purchase #7	$53.39	11.571%	$59.5678	$59.57	$59.55	$59.60
7 purchase totals =	$843.87		$930.5534	$930.55	$930.50	$930.60