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	$230.63	8.520%	$250.2797	$250.28	$250.30	$250.30
Purchase #2	$18.67	13.693%	$21.2265	$21.23	$21.25	$21.20
Purchase #3	$53.47	10.507%	$59.0881	$59.09	$59.10	$59.10
Purchase #4	$12.48	12.802%	$14.0777	$14.08	$14.10	$14.10
Purchase #5	$37.61	11.466%	$41.9224	$41.92	$41.90	$41.90
Purchase #6	$180.29	10.187%	$198.6561	$198.66	$198.65	$198.70
Purchase #7	$232.56	13.538%	$264.044	$264.04	$264.05	$264.00
7 purchase totals =	$765.71		$849.2945	$849.30	$849.35	$849.30