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	$184.38	6.287%	$195.972	$195.97	$195.95	$196.00
Purchase #2	$17.87	5.152%	$18.7907	$18.79	$18.80	$18.80
Purchase #3	$165.76	10.105%	$182.51	$182.51	$182.50	$182.50
Purchase #4	$96.32	5.816%	$101.922	$101.92	$101.90	$101.90
Purchase #5	$171.81	11.155%	$190.9754	$190.98	$191.00	$191.00
Purchase #6	$248.61	13.864%	$283.0773	$283.08	$283.10	$283.10
Purchase #7	$18.50	8.764%	$20.1213	$20.12	$20.10	$20.10
7 purchase totals =	$903.25		$993.3687	$993.37	$993.35	$993.40