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	$155.50	5.708%	$164.3759	$164.38	$164.40	$164.40
Purchase #2	$48.95	4.479%	$51.1425	$51.14	$51.15	$51.10
Purchase #3	$97.91	13.754%	$111.3765	$111.38	$111.40	$111.40
Purchase #4	$67.97	9.268%	$74.2695	$74.27	$74.25	$74.30
Purchase #5	$247.66	4.102%	$257.819	$257.82	$257.80	$257.80
Purchase #6	$243.30	13.226%	$275.4789	$275.48	$275.50	$275.50
Purchase #7	$75.89	4.186%	$79.0668	$79.07	$79.05	$79.10
7 purchase totals =	$937.18		$1,013.5291	$1,013.54	$1,013.55	$1,013.60