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	$152.63	12.447%	$171.6279	$171.63	$171.65	$171.60
Purchase #2	$12.43	5.561%	$13.1212	$13.12	$13.10	$13.10
Purchase #3	$44.59	10.578%	$49.3067	$49.31	$49.30	$49.30
Purchase #4	$63.83	13.134%	$72.2134	$72.21	$72.20	$72.20
Purchase #5	$18.28	11.138%	$20.316	$20.32	$20.30	$20.30
Purchase #6	$208.49	8.839%	$226.9184	$226.92	$226.90	$226.90
Purchase #7	$52.32	12.755%	$58.9934	$58.99	$59.00	$59.00
7 purchase totals =	$552.57		$612.4970	$612.50	$612.45	$612.40