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	$164.87	4.590%	$172.4375	$172.44	$172.45	$172.40
Purchase #2	$45.85	12.374%	$51.5235	$51.52	$51.50	$51.50
Purchase #3	$195.72	8.797%	$212.9375	$212.94	$212.95	$212.90
Purchase #4	$73.82	5.123%	$77.6018	$77.60	$77.60	$77.60
Purchase #5	$149.78	11.303%	$166.7096	$166.71	$166.70	$166.70
Purchase #6	$35.31	12.595%	$39.7573	$39.76	$39.75	$39.80
Purchase #7	$92.96	11.410%	$103.5667	$103.57	$103.55	$103.60
7 purchase totals =	$758.31		$824.5339	$824.54	$824.50	$824.50