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	$64.71	4.750%	$67.7837	$67.78	$67.80	$67.80
Purchase #2	$217.94	9.438%	$238.5092	$238.51	$238.50	$238.50
Purchase #3	$202.78	3.340%	$209.5529	$209.55	$209.55	$209.60
Purchase #4	$133.33	9.612%	$146.1457	$146.15	$146.15	$146.10
Purchase #5	$29.50	7.462%	$31.7013	$31.70	$31.70	$31.70
Purchase #6	$228.96	6.667%	$244.2248	$244.22	$244.20	$244.20
Purchase #7	$67.67	10.698%	$74.9093	$74.91	$74.90	$74.90
7 purchase totals =	$944.89		$1,012.8269	$1,012.82	$1,012.80	$1,012.80