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	$57.90	5.477%	$61.0712	$61.07	$61.05	$61.10
Purchase #2	$31.62	13.605%	$35.9219	$35.92	$35.90	$35.90
Purchase #3	$81.41	12.428%	$91.5276	$91.53	$91.55	$91.50
Purchase #4	$40.52	13.187%	$45.8634	$45.86	$45.85	$45.90
Purchase #5	$112.72	4.143%	$117.39	$117.39	$117.40	$117.40
Purchase #6	$96.79	7.109%	$103.6708	$103.67	$103.65	$103.70
Purchase #7	$155.92	8.107%	$168.5604	$168.56	$168.55	$168.60
7 purchase totals =	$576.88		$624.0053	$624.00	$623.95	$624.10