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	$243.37	4.413%	$254.1099	$254.11	$254.10	$254.10
Purchase #2	$103.72	7.861%	$111.8734	$111.87	$111.85	$111.90
Purchase #3	$96.53	4.563%	$100.9347	$100.93	$100.95	$100.90
Purchase #4	$36.50	7.573%	$39.2641	$39.26	$39.25	$39.30
Purchase #5	$140.91	12.287%	$158.2236	$158.22	$158.20	$158.20
Purchase #6	$155.73	10.160%	$171.5522	$171.55	$171.55	$171.60
Purchase #7	$108.54	9.627%	$118.9891	$118.99	$119.00	$119.00
7 purchase totals =	$885.30		$954.9470	$954.93	$954.90	$955.00