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	$109.87	13.754%	$124.9815	$124.98	$125.00	$125.00
Purchase #2	$87.29	3.476%	$90.3242	$90.32	$90.30	$90.30
Purchase #3	$235.39	3.192%	$242.9036	$242.90	$242.90	$242.90
Purchase #4	$32.38	13.412%	$36.7228	$36.72	$36.70	$36.70
Purchase #5	$68.85	3.822%	$71.4814	$71.48	$71.50	$71.50
Purchase #6	$53.56	4.401%	$55.9172	$55.92	$55.90	$55.90
Purchase #7	$165.43	13.573%	$187.8838	$187.88	$187.90	$187.90
7 purchase totals =	$752.77		$810.2145	$810.20	$810.20	$810.20