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	$168.62	12.224%	$189.2321	$189.23	$189.25	$189.20
Purchase #2	$176.48	7.714%	$190.0937	$190.09	$190.10	$190.10
Purchase #3	$131.89	12.461%	$148.3248	$148.32	$148.30	$148.30
Purchase #4	$67.34	9.864%	$73.9824	$73.98	$74.00	$74.00
Purchase #5	$196.61	13.177%	$222.5173	$222.52	$222.50	$222.50
Purchase #6	$248.41	5.792%	$262.7979	$262.80	$262.80	$262.80
Purchase #7	$25.47	11.830%	$28.4831	$28.48	$28.50	$28.50
7 purchase totals =	$1,014.82		$1,115.4313	$1,115.42	$1,115.45	$1,115.40