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	$148.50	12.832%	$167.5555	$167.56	$167.55	$167.60
Purchase #2	$71.60	6.442%	$76.2125	$76.21	$76.20	$76.20
Purchase #3	$65.69	11.241%	$73.0742	$73.07	$73.05	$73.10
Purchase #4	$75.74	10.104%	$83.3928	$83.39	$83.40	$83.40
Purchase #5	$61.51	8.150%	$66.5231	$66.52	$66.50	$66.50
Purchase #6	$249.97	11.794%	$279.4515	$279.45	$279.45	$279.50
Purchase #7	$202.73	9.788%	$222.5732	$222.57	$222.55	$222.60
7 purchase totals =	$875.74		$968.7828	$968.77	$968.70	$968.90