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	$175.50	13.451%	$199.1065	$199.11	$199.10	$199.10
Purchase #2	$73.92	6.582%	$78.7854	$78.79	$78.80	$78.80
Purchase #3	$222.90	6.267%	$236.8691	$236.87	$236.85	$236.90
Purchase #4	$216.72	6.798%	$231.4526	$231.45	$231.45	$231.50
Purchase #5	$245.42	4.360%	$256.1203	$256.12	$256.10	$256.10
Purchase #6	$237.37	12.233%	$266.4075	$266.41	$266.40	$266.40
Purchase #7	$166.82	7.400%	$179.1647	$179.16	$179.15	$179.20
7 purchase totals =	$1,338.65		$1,447.9061	$1,447.91	$1,447.85	$1,448.00