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	$245.59	4.411%	$256.423	$256.42	$256.40	$256.40
Purchase #2	$42.78	7.313%	$45.9085	$45.91	$45.90	$45.90
Purchase #3	$118.32	10.627%	$130.8939	$130.89	$130.90	$130.90
Purchase #4	$162.73	13.762%	$185.1249	$185.12	$185.10	$185.10
Purchase #5	$95.41	11.582%	$106.4604	$106.46	$106.45	$106.50
Purchase #6	$21.80	13.639%	$24.7733	$24.77	$24.75	$24.80
Purchase #7	$176.94	6.448%	$188.3491	$188.35	$188.35	$188.30
7 purchase totals =	$863.57		$937.9331	$937.92	$937.85	$937.90