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	$82.30	13.141%	$93.115	$93.12	$93.10	$93.10
Purchase #2	$32.60	9.430%	$35.6742	$35.67	$35.65	$35.70
Purchase #3	$110.78	3.158%	$114.2784	$114.28	$114.30	$114.30
Purchase #4	$77.31	8.272%	$83.7051	$83.71	$83.70	$83.70
Purchase #5	$165.33	5.520%	$174.4562	$174.46	$174.45	$174.50
Purchase #6	$121.49	8.167%	$131.4121	$131.41	$131.40	$131.40
Purchase #7	$90.90	9.381%	$99.4273	$99.43	$99.45	$99.40
7 purchase totals =	$680.71		$732.0683	$732.08	$732.05	$732.10