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	$207.48	4.375%	$216.5573	$216.56	$216.55	$216.60
Purchase #2	$62.34	8.347%	$67.5435	$67.54	$67.55	$67.50
Purchase #3	$233.93	4.741%	$245.0206	$245.02	$245.00	$245.00
Purchase #4	$138.95	6.198%	$147.5621	$147.56	$147.55	$147.60
Purchase #5	$124.41	13.443%	$141.1344	$141.13	$141.15	$141.10
Purchase #6	$161.85	6.315%	$172.0708	$172.07	$172.05	$172.10
Purchase #7	$92.95	3.155%	$95.8826	$95.88	$95.90	$95.90
7 purchase totals =	$1,021.91		$1,085.7713	$1,085.76	$1,085.75	$1,085.80