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	$177.73	10.438%	$196.2815	$196.28	$196.30	$196.30
Purchase #2	$115.82	3.804%	$120.2258	$120.23	$120.25	$120.20
Purchase #3	$116.83	11.576%	$130.3542	$130.35	$130.35	$130.40
Purchase #4	$115.34	9.869%	$126.7229	$126.72	$126.70	$126.70
Purchase #5	$37.31	7.443%	$40.087	$40.09	$40.10	$40.10
Purchase #6	$56.66	5.593%	$59.829	$59.83	$59.85	$59.80
Purchase #7	$24.61	6.790%	$26.281	$26.28	$26.30	$26.30
7 purchase totals =	$644.30		$699.7814	$699.78	$699.85	$699.80