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	$200.56	12.468%	$225.5658	$225.57	$225.55	$225.60
Purchase #2	$159.73	7.788%	$172.1698	$172.17	$172.15	$172.20
Purchase #3	$235.59	7.794%	$253.9519	$253.95	$253.95	$254.00
Purchase #4	$47.63	6.697%	$50.8198	$50.82	$50.80	$50.80
Purchase #5	$240.91	6.800%	$257.2919	$257.29	$257.30	$257.30
Purchase #6	$33.74	12.354%	$37.9082	$37.91	$37.90	$37.90
Purchase #7	$177.93	5.477%	$187.6752	$187.68	$187.70	$187.70
7 purchase totals =	$1,096.09		$1,185.3826	$1,185.39	$1,185.35	$1,185.50