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	$189.26	3.565%	$196.0071	$196.01	$196.00	$196.00
Purchase #2	$58.99	6.463%	$62.8025	$62.80	$62.80	$62.80
Purchase #3	$242.29	3.317%	$250.3268	$250.33	$250.35	$250.30
Purchase #4	$15.82	13.457%	$17.9489	$17.95	$17.95	$17.90
Purchase #5	$213.42	8.494%	$231.5479	$231.55	$231.55	$231.50
Purchase #6	$56.50	4.433%	$59.0046	$59.00	$59.00	$59.00
Purchase #7	$42.31	9.595%	$46.3696	$46.37	$46.35	$46.40
7 purchase totals =	$818.59		$864.0074	$864.01	$864.00	$863.90