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	$53.89	11.811%	$60.2549	$60.25	$60.25	$60.30
Purchase #2	$69.33	3.719%	$71.9084	$71.91	$71.90	$71.90
Purchase #3	$131.47	10.471%	$145.2362	$145.24	$145.25	$145.20
Purchase #4	$45.56	6.452%	$48.4995	$48.50	$48.50	$48.50
Purchase #5	$243.68	10.684%	$269.7148	$269.71	$269.70	$269.70
Purchase #6	$106.28	13.189%	$120.2973	$120.30	$120.30	$120.30
Purchase #7	$177.59	7.805%	$191.4509	$191.45	$191.45	$191.50
7 purchase totals =	$827.80		$907.3620	$907.36	$907.35	$907.40