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	$93.52	10.254%	$103.1095	$103.11	$103.10	$103.10
Purchase #2	$163.43	6.117%	$173.427	$173.43	$173.45	$173.40
Purchase #3	$224.53	6.133%	$238.3004	$238.30	$238.30	$238.30
Purchase #4	$28.29	13.145%	$32.0087	$32.01	$32.00	$32.00
Purchase #5	$54.27	12.706%	$61.1655	$61.17	$61.15	$61.20
Purchase #6	$68.61	5.347%	$72.2786	$72.28	$72.30	$72.30
Purchase #7	$54.50	8.386%	$59.0704	$59.07	$59.05	$59.10
7 purchase totals =	$687.15		$739.3601	$739.37	$739.35	$739.40