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	$138.98	10.748%	$153.9176	$153.92	$153.90	$153.90
Purchase #2	$73.96	6.365%	$78.6676	$78.67	$78.65	$78.70
Purchase #3	$222.92	11.334%	$248.1858	$248.19	$248.20	$248.20
Purchase #4	$86.54	12.624%	$97.4648	$97.46	$97.45	$97.50
Purchase #5	$83.64	6.733%	$89.2715	$89.27	$89.25	$89.30
Purchase #6	$41.52	10.135%	$45.7281	$45.73	$45.75	$45.70
Purchase #7	$52.91	13.831%	$60.228	$60.23	$60.25	$60.20
7 purchase totals =	$700.47		$773.4634	$773.47	$773.45	$773.50