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	$60.94	3.821%	$63.2685	$63.27	$63.25	$63.30
Purchase #2	$195.45	11.500%	$217.9268	$217.93	$217.95	$217.90
Purchase #3	$57.44	7.112%	$61.5251	$61.53	$61.55	$61.50
Purchase #4	$30.25	13.299%	$34.2729	$34.27	$34.25	$34.30
Purchase #5	$30.94	8.352%	$33.5241	$33.52	$33.50	$33.50
Purchase #6	$51.68	3.216%	$53.342	$53.34	$53.35	$53.30
Purchase #7	$131.48	11.668%	$146.8211	$146.82	$146.80	$146.80
7 purchase totals =	$558.18		$610.6805	$610.68	$610.65	$610.60