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	$191.50	9.637%	$209.9549	$209.95	$209.95	$210.00
Purchase #2	$34.64	8.157%	$37.4656	$37.47	$37.45	$37.50
Purchase #3	$26.61	12.335%	$29.8923	$29.89	$29.90	$29.90
Purchase #4	$90.89	6.621%	$96.9078	$96.91	$96.90	$96.90
Purchase #5	$27.68	13.858%	$31.5159	$31.52	$31.50	$31.50
Purchase #6	$15.46	12.714%	$17.4256	$17.43	$17.45	$17.40
Purchase #7	$97.82	9.281%	$106.8987	$106.90	$106.90	$106.90
7 purchase totals =	$484.60		$530.0608	$530.07	$530.05	$530.10