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	$200.32	8.157%	$216.6601	$216.66	$216.65	$216.70
Purchase #2	$45.88	10.418%	$50.6598	$50.66	$50.65	$50.70
Purchase #3	$72.28	12.278%	$81.1545	$81.15	$81.15	$81.20
Purchase #4	$179.44	5.171%	$188.7188	$188.72	$188.70	$188.70
Purchase #5	$52.85	11.706%	$59.0366	$59.04	$59.05	$59.00
Purchase #6	$135.27	9.392%	$147.9746	$147.97	$147.95	$148.00
Purchase #7	$158.50	13.328%	$179.6249	$179.62	$179.60	$179.60
7 purchase totals =	$844.54		$923.8293	$923.82	$923.75	$923.90