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	$138.83	8.180%	$150.1863	$150.19	$150.20	$150.20
Purchase #2	$234.55	13.332%	$265.8202	$265.82	$265.80	$265.80
Purchase #3	$172.27	12.625%	$194.0191	$194.02	$194.00	$194.00
Purchase #4	$40.73	12.208%	$45.7023	$45.70	$45.70	$45.70
Purchase #5	$75.28	13.850%	$85.7063	$85.71	$85.70	$85.70
Purchase #6	$98.56	13.545%	$111.91	$111.91	$111.90	$111.90
Purchase #7	$176.91	8.521%	$191.9845	$191.98	$192.00	$192.00
7 purchase totals =	$937.13		$1,045.3287	$1,045.33	$1,045.30	$1,045.30