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	$123.46	7.281%	$132.4491	$132.45	$132.45	$132.40
Purchase #2	$202.52	4.356%	$211.3418	$211.34	$211.35	$211.30
Purchase #3	$127.77	11.757%	$142.7919	$142.79	$142.80	$142.80
Purchase #4	$33.43	10.599%	$36.9732	$36.97	$36.95	$37.00
Purchase #5	$169.89	10.118%	$187.0795	$187.08	$187.10	$187.10
Purchase #6	$231.27	10.311%	$255.1162	$255.12	$255.10	$255.10
Purchase #7	$95.68	7.702%	$103.0493	$103.05	$103.05	$103.00
7 purchase totals =	$984.02		$1,068.8010	$1,068.80	$1,068.80	$1,068.70