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	$209.34	13.470%	$237.5381	$237.54	$237.55	$237.50
Purchase #2	$224.32	5.619%	$236.9245	$236.92	$236.90	$236.90
Purchase #3	$195.79	8.171%	$211.788	$211.79	$211.80	$211.80
Purchase #4	$42.98	6.832%	$45.9164	$45.92	$45.90	$45.90
Purchase #5	$50.71	12.506%	$57.0518	$57.05	$57.05	$57.10
Purchase #6	$217.35	7.485%	$233.6186	$233.62	$233.60	$233.60
Purchase #7	$128.76	13.307%	$145.8941	$145.89	$145.90	$145.90
7 purchase totals =	$1,069.25		$1,168.7315	$1,168.73	$1,168.70	$1,168.70