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	$194.71	12.319%	$218.6963	$218.70	$218.70	$218.70
Purchase #2	$116.28	9.541%	$127.3743	$127.37	$127.35	$127.40
Purchase #3	$226.66	3.363%	$234.2826	$234.28	$234.30	$234.30
Purchase #4	$95.89	13.708%	$109.0346	$109.03	$109.05	$109.00
Purchase #5	$224.33	11.838%	$250.8862	$250.89	$250.90	$250.90
Purchase #6	$9.59	9.870%	$10.5365	$10.54	$10.55	$10.50
Purchase #7	$156.48	6.351%	$166.418	$166.42	$166.40	$166.40
7 purchase totals =	$1,023.94		$1,117.2285	$1,117.23	$1,117.25	$1,117.20