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	$147.53	13.806%	$167.898	$167.90	$167.90	$167.90
Purchase #2	$103.50	9.457%	$113.288	$113.29	$113.30	$113.30
Purchase #3	$234.48	8.821%	$255.1635	$255.16	$255.15	$255.20
Purchase #4	$169.49	3.782%	$175.9001	$175.90	$175.90	$175.90
Purchase #5	$7.32	12.804%	$8.2573	$8.26	$8.25	$8.30
Purchase #6	$24.79	13.853%	$28.2242	$28.22	$28.20	$28.20
Purchase #7	$242.89	9.170%	$265.163	$265.16	$265.15	$265.20
7 purchase totals =	$930.00		$1,013.8941	$1,013.89	$1,013.85	$1,014.00