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	$182.57	7.800%	$196.8105	$196.81	$196.80	$196.80
Purchase #2	$53.33	12.719%	$60.113	$60.11	$60.10	$60.10
Purchase #3	$226.84	13.316%	$257.046	$257.05	$257.05	$257.00
Purchase #4	$29.72	10.527%	$32.8486	$32.85	$32.85	$32.80
Purchase #5	$116.43	9.489%	$127.478	$127.48	$127.50	$127.50
Purchase #6	$127.32	13.229%	$144.1632	$144.16	$144.15	$144.20
Purchase #7	$143.30	11.151%	$159.2794	$159.28	$159.30	$159.30
7 purchase totals =	$879.51		$977.7387	$977.74	$977.75	$977.70