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	$119.31	9.428%	$130.5585	$130.56	$130.55	$130.60
Purchase #2	$209.63	3.102%	$216.1327	$216.13	$216.15	$216.10
Purchase #3	$55.90	4.357%	$58.3356	$58.34	$58.35	$58.30
Purchase #4	$67.66	4.315%	$70.5795	$70.58	$70.60	$70.60
Purchase #5	$194.74	7.118%	$208.6016	$208.60	$208.60	$208.60
Purchase #6	$120.29	9.331%	$131.5143	$131.51	$131.50	$131.50
Purchase #7	$191.33	12.808%	$215.8355	$215.84	$215.85	$215.80
7 purchase totals =	$958.86		$1,031.5577	$1,031.56	$1,031.60	$1,031.50