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	$22.32	12.353%	$25.0772	$25.08	$25.10	$25.10
Purchase #2	$71.63	9.817%	$78.6619	$78.66	$78.65	$78.70
Purchase #3	$26.70	6.319%	$28.3872	$28.39	$28.40	$28.40
Purchase #4	$87.42	4.452%	$91.3119	$91.31	$91.30	$91.30
Purchase #5	$31.92	4.167%	$33.2501	$33.25	$33.25	$33.30
Purchase #6	$29.35	7.748%	$31.624	$31.62	$31.60	$31.60
Purchase #7	$194.33	11.635%	$216.9403	$216.94	$216.95	$216.90
7 purchase totals =	$463.67		$505.2526	$505.25	$505.25	$505.30