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	$170.63	8.855%	$185.7393	$185.74	$185.75	$185.70
Purchase #2	$81.51	5.724%	$86.1756	$86.18	$86.20	$86.20
Purchase #3	$132.73	10.580%	$146.7728	$146.77	$146.75	$146.80
Purchase #4	$146.46	12.725%	$165.097	$165.10	$165.10	$165.10
Purchase #5	$18.36	11.730%	$20.5136	$20.51	$20.50	$20.50
Purchase #6	$244.91	8.292%	$265.2179	$265.22	$265.20	$265.20
Purchase #7	$78.71	9.796%	$86.4204	$86.42	$86.40	$86.40
7 purchase totals =	$873.31		$955.9366	$955.94	$955.90	$955.90