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	$55.32	11.123%	$61.4732	$61.47	$61.45	$61.50
Purchase #2	$111.40	8.693%	$121.084	$121.08	$121.10	$121.10
Purchase #3	$82.39	8.665%	$89.5291	$89.53	$89.55	$89.50
Purchase #4	$147.48	9.613%	$161.6573	$161.66	$161.65	$161.70
Purchase #5	$135.58	12.484%	$152.5058	$152.51	$152.50	$152.50
Purchase #6	$152.30	9.827%	$167.2665	$167.27	$167.25	$167.30
Purchase #7	$127.39	13.346%	$144.3915	$144.39	$144.40	$144.40
7 purchase totals =	$811.86		$897.9074	$897.91	$897.90	$898.00