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	$149.55	10.535%	$165.3051	$165.31	$165.30	$165.30
Purchase #2	$37.98	9.805%	$41.7039	$41.70	$41.70	$41.70
Purchase #3	$143.47	5.466%	$151.3121	$151.31	$151.30	$151.30
Purchase #4	$162.70	10.799%	$180.27	$180.27	$180.25	$180.30
Purchase #5	$76.55	6.384%	$81.437	$81.44	$81.45	$81.40
Purchase #6	$88.61	13.150%	$100.2622	$100.26	$100.25	$100.30
Purchase #7	$18.48	10.328%	$20.3886	$20.39	$20.40	$20.40
7 purchase totals =	$677.34		$740.6789	$740.68	$740.65	$740.70