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	$130.50	6.794%	$139.3662	$139.37	$139.35	$139.40
Purchase #2	$164.71	4.680%	$172.4184	$172.42	$172.40	$172.40
Purchase #3	$158.95	11.413%	$177.091	$177.09	$177.10	$177.10
Purchase #4	$89.63	4.333%	$93.5137	$93.51	$93.50	$93.50
Purchase #5	$36.95	3.623%	$38.2887	$38.29	$38.30	$38.30
Purchase #6	$185.59	9.650%	$203.4994	$203.50	$203.50	$203.50
Purchase #7	$213.53	4.194%	$222.4854	$222.49	$222.50	$222.50
7 purchase totals =	$979.86		$1,046.6628	$1,046.67	$1,046.65	$1,046.70