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	$77.67	7.182%	$83.2483	$83.25	$83.25	$83.20
Purchase #2	$49.82	9.281%	$54.4438	$54.44	$54.45	$54.40
Purchase #3	$168.37	11.253%	$187.3167	$187.32	$187.30	$187.30
Purchase #4	$132.89	9.192%	$145.1052	$145.11	$145.10	$145.10
Purchase #5	$250.34	11.179%	$278.3255	$278.33	$278.35	$278.30
Purchase #6	$141.83	13.309%	$160.7062	$160.71	$160.70	$160.70
Purchase #7	$189.68	7.339%	$203.6006	$203.60	$203.60	$203.60
7 purchase totals =	$1,010.60		$1,112.7463	$1,112.76	$1,112.75	$1,112.60