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	$48.68	4.250%	$50.7489	$50.75	$50.75	$50.70
Purchase #2	$71.49	11.715%	$79.8651	$79.87	$79.85	$79.90
Purchase #3	$91.54	3.528%	$94.7695	$94.77	$94.75	$94.80
Purchase #4	$20.69	5.871%	$21.9047	$21.90	$21.90	$21.90
Purchase #5	$199.64	6.826%	$213.2674	$213.27	$213.25	$213.30
Purchase #6	$95.73	6.200%	$101.6653	$101.67	$101.65	$101.70
Purchase #7	$78.73	13.274%	$89.1806	$89.18	$89.20	$89.20
7 purchase totals =	$606.50		$651.4015	$651.41	$651.35	$651.50