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	$61.85	9.285%	$67.5928	$67.59	$67.60	$67.60
Purchase #2	$140.49	4.197%	$146.3864	$146.39	$146.40	$146.40
Purchase #3	$120.62	6.496%	$128.4555	$128.46	$128.45	$128.50
Purchase #4	$249.29	6.172%	$264.6762	$264.68	$264.70	$264.70
Purchase #5	$122.43	8.215%	$132.4876	$132.49	$132.50	$132.50
Purchase #6	$7.59	10.133%	$8.3591	$8.36	$8.35	$8.40
Purchase #7	$98.55	6.581%	$105.0356	$105.04	$105.05	$105.00
7 purchase totals =	$800.82		$852.9932	$853.01	$853.05	$853.10