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	$135.97	10.584%	$150.3611	$150.36	$150.35	$150.40
Purchase #2	$26.81	9.323%	$29.3095	$29.31	$29.30	$29.30
Purchase #3	$220.51	5.796%	$233.2908	$233.29	$233.30	$233.30
Purchase #4	$127.83	10.676%	$141.4771	$141.48	$141.50	$141.50
Purchase #5	$173.48	10.733%	$192.0996	$192.10	$192.10	$192.10
Purchase #6	$89.66	3.234%	$92.5596	$92.56	$92.55	$92.60
Purchase #7	$203.52	9.699%	$223.2594	$223.26	$223.25	$223.30
7 purchase totals =	$977.78		$1,062.3571	$1,062.36	$1,062.35	$1,062.50