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	$83.25	8.518%	$90.3412	$90.34	$90.35	$90.30
Purchase #2	$92.76	7.327%	$99.5565	$99.56	$99.55	$99.60
Purchase #3	$65.71	8.233%	$71.1199	$71.12	$71.10	$71.10
Purchase #4	$66.89	5.566%	$70.6131	$70.61	$70.60	$70.60
Purchase #5	$79.45	7.212%	$85.1799	$85.18	$85.20	$85.20
Purchase #6	$76.69	11.213%	$85.2892	$85.29	$85.30	$85.30
Purchase #7	$237.41	5.447%	$250.3417	$250.34	$250.35	$250.30
7 purchase totals =	$702.16		$752.4415	$752.44	$752.45	$752.40