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	$233.70	10.315%	$257.8062	$257.81	$257.80	$257.80
Purchase #2	$30.74	9.747%	$33.7362	$33.74	$33.75	$33.70
Purchase #3	$121.32	7.379%	$130.2722	$130.27	$130.25	$130.30
Purchase #4	$248.61	6.521%	$264.8219	$264.82	$264.80	$264.80
Purchase #5	$185.65	7.260%	$199.1282	$199.13	$199.15	$199.10
Purchase #6	$38.51	10.404%	$42.5166	$42.52	$42.50	$42.50
Purchase #7	$40.82	10.619%	$45.1547	$45.15	$45.15	$45.20
7 purchase totals =	$899.35		$973.4360	$973.44	$973.40	$973.40