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	$95.66	10.248%	$105.4632	$105.46	$105.45	$105.50
Purchase #2	$238.25	7.810%	$256.8573	$256.86	$256.85	$256.90
Purchase #3	$22.48	5.413%	$23.6968	$23.70	$23.70	$23.70
Purchase #4	$137.64	6.466%	$146.5398	$146.54	$146.55	$146.50
Purchase #5	$66.48	7.455%	$71.4361	$71.44	$71.45	$71.40
Purchase #6	$130.66	9.788%	$143.449	$143.45	$143.45	$143.40
Purchase #7	$31.69	11.310%	$35.2741	$35.27	$35.25	$35.30
7 purchase totals =	$722.86		$782.7163	$782.72	$782.70	$782.70