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	$125.35	3.712%	$130.003	$130.00	$130.00	$130.00
Purchase #2	$30.92	7.639%	$33.282	$33.28	$33.30	$33.30
Purchase #3	$211.88	10.106%	$233.2926	$233.29	$233.30	$233.30
Purchase #4	$68.34	6.695%	$72.9154	$72.92	$72.90	$72.90
Purchase #5	$16.55	11.523%	$18.4571	$18.46	$18.45	$18.50
Purchase #6	$231.38	12.755%	$260.8925	$260.89	$260.90	$260.90
Purchase #7	$82.98	5.775%	$87.7721	$87.77	$87.75	$87.80
7 purchase totals =	$767.40		$836.6147	$836.61	$836.60	$836.70