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	$131.47	11.256%	$146.2683	$146.27	$146.25	$146.30
Purchase #2	$69.39	4.267%	$72.3509	$72.35	$72.35	$72.40
Purchase #3	$17.63	4.484%	$18.4205	$18.42	$18.40	$18.40
Purchase #4	$42.53	6.737%	$45.3952	$45.40	$45.40	$45.40
Purchase #5	$91.49	6.152%	$97.1185	$97.12	$97.10	$97.10
Purchase #6	$76.43	8.156%	$82.6636	$82.66	$82.65	$82.70
Purchase #7	$202.73	12.221%	$227.5056	$227.51	$227.50	$227.50
7 purchase totals =	$631.67		$689.7226	$689.73	$689.65	$689.80