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	$88.48	13.254%	$100.2071	$100.21	$100.20	$100.20
Purchase #2	$11.59	10.189%	$12.7709	$12.77	$12.75	$12.80
Purchase #3	$123.92	12.631%	$139.5723	$139.57	$139.55	$139.60
Purchase #4	$65.65	11.650%	$73.2982	$73.30	$73.30	$73.30
Purchase #5	$84.96	12.419%	$95.5112	$95.51	$95.50	$95.50
Purchase #6	$22.76	11.336%	$25.3401	$25.34	$25.35	$25.30
Purchase #7	$54.37	7.729%	$58.5723	$58.57	$58.55	$58.60
7 purchase totals =	$451.73		$505.2721	$505.27	$505.20	$505.30