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	$14.54	9.560%	$15.93	$15.93	$15.95	$15.90
Purchase #2	$62.55	6.857%	$66.8391	$66.84	$66.85	$66.80
Purchase #3	$55.32	7.795%	$59.6322	$59.63	$59.65	$59.60
Purchase #4	$64.48	5.658%	$68.1283	$68.13	$68.15	$68.10
Purchase #5	$52.27	9.327%	$57.1452	$57.15	$57.15	$57.10
Purchase #6	$37.86	5.713%	$40.0229	$40.02	$40.00	$40.00
Purchase #7	$206.93	9.856%	$227.325	$227.33	$227.35	$227.30
7 purchase totals =	$493.95		$535.0227	$535.03	$535.10	$534.80