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	$57.95	5.817%	$61.321	$61.32	$61.30	$61.30
Purchase #2	$215.28	8.715%	$234.0417	$234.04	$234.05	$234.00
Purchase #3	$101.73	11.458%	$113.3862	$113.39	$113.40	$113.40
Purchase #4	$162.34	4.850%	$170.2135	$170.21	$170.20	$170.20
Purchase #5	$106.53	4.593%	$111.4229	$111.42	$111.40	$111.40
Purchase #6	$81.44	8.757%	$88.5717	$88.57	$88.55	$88.60
Purchase #7	$32.37	3.611%	$33.5389	$33.54	$33.55	$33.50
7 purchase totals =	$757.64		$812.4959	$812.49	$812.45	$812.40