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	$225.75	7.799%	$243.3562	$243.36	$243.35	$243.40
Purchase #2	$83.30	4.171%	$86.7744	$86.77	$86.75	$86.80
Purchase #3	$158.79	7.517%	$170.7262	$170.73	$170.75	$170.70
Purchase #4	$74.77	4.259%	$77.9545	$77.95	$77.95	$78.00
Purchase #5	$41.61	10.158%	$45.8367	$45.84	$45.85	$45.80
Purchase #6	$125.94	10.634%	$139.3325	$139.33	$139.35	$139.30
Purchase #7	$226.56	12.743%	$255.4305	$255.43	$255.45	$255.40
7 purchase totals =	$936.72		$1,019.4110	$1,019.41	$1,019.45	$1,019.40