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	$74.91	10.375%	$82.6819	$82.68	$82.70	$82.70
Purchase #2	$168.78	11.585%	$188.3332	$188.33	$188.35	$188.30
Purchase #3	$66.26	8.202%	$71.6946	$71.69	$71.70	$71.70
Purchase #4	$220.25	13.466%	$249.9089	$249.91	$249.90	$249.90
Purchase #5	$76.90	11.145%	$85.4705	$85.47	$85.45	$85.50
Purchase #6	$232.93	7.376%	$250.1109	$250.11	$250.10	$250.10
Purchase #7	$206.71	13.528%	$234.6737	$234.67	$234.65	$234.70
7 purchase totals =	$1,046.74		$1,162.8737	$1,162.86	$1,162.85	$1,162.90