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	$153.85	4.333%	$160.5163	$160.52	$160.50	$160.50
Purchase #2	$210.74	9.753%	$231.2935	$231.29	$231.30	$231.30
Purchase #3	$209.88	13.117%	$237.41	$237.41	$237.40	$237.40
Purchase #4	$73.53	6.863%	$78.5764	$78.58	$78.60	$78.60
Purchase #5	$36.69	7.603%	$39.4795	$39.48	$39.50	$39.50
Purchase #6	$208.96	5.181%	$219.7862	$219.79	$219.80	$219.80
Purchase #7	$140.54	3.479%	$145.4294	$145.43	$145.45	$145.40
7 purchase totals =	$1,034.19		$1,112.4913	$1,112.50	$1,112.55	$1,112.50