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	$101.87	7.829%	$109.8454	$109.85	$109.85	$109.80
Purchase #2	$214.66	3.298%	$221.7395	$221.74	$221.75	$221.70
Purchase #3	$67.89	13.843%	$77.288	$77.29	$77.30	$77.30
Purchase #4	$151.52	10.834%	$167.9357	$167.94	$167.95	$167.90
Purchase #5	$189.62	12.710%	$213.7207	$213.72	$213.70	$213.70
Purchase #6	$40.71	7.666%	$43.8308	$43.83	$43.85	$43.80
Purchase #7	$110.85	6.576%	$118.1395	$118.14	$118.15	$118.10
7 purchase totals =	$877.12		$952.4996	$952.51	$952.55	$952.30