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	$160.31	3.188%	$165.4207	$165.42	$165.40	$165.40
Purchase #2	$115.91	6.411%	$123.341	$123.34	$123.35	$123.30
Purchase #3	$213.72	12.418%	$240.2597	$240.26	$240.25	$240.30
Purchase #4	$169.89	7.634%	$182.8594	$182.86	$182.85	$182.90
Purchase #5	$24.69	5.347%	$26.0102	$26.01	$26.00	$26.00
Purchase #6	$78.57	8.843%	$85.5179	$85.52	$85.50	$85.50
Purchase #7	$202.98	10.268%	$223.822	$223.82	$223.80	$223.80
7 purchase totals =	$966.07		$1,047.2309	$1,047.23	$1,047.15	$1,047.20