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	$209.70	10.360%	$231.4249	$231.42	$231.40	$231.40
Purchase #2	$78.45	10.518%	$86.7014	$86.70	$86.70	$86.70
Purchase #3	$147.53	5.261%	$155.2916	$155.29	$155.30	$155.30
Purchase #4	$236.35	9.388%	$258.5385	$258.54	$258.55	$258.50
Purchase #5	$28.55	11.668%	$31.8812	$31.88	$31.90	$31.90
Purchase #6	$229.63	12.142%	$257.5117	$257.51	$257.50	$257.50
Purchase #7	$140.33	4.350%	$146.4344	$146.43	$146.45	$146.40
7 purchase totals =	$1,070.54		$1,167.7837	$1,167.77	$1,167.80	$1,167.70