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	$188.95	13.651%	$214.7436	$214.74	$214.75	$214.70
Purchase #2	$41.91	11.724%	$46.8235	$46.82	$46.80	$46.80
Purchase #3	$249.78	13.684%	$283.9599	$283.96	$283.95	$284.00
Purchase #4	$170.63	8.749%	$185.5584	$185.56	$185.55	$185.60
Purchase #5	$141.57	9.805%	$155.4509	$155.45	$155.45	$155.50
Purchase #6	$157.42	3.488%	$162.9108	$162.91	$162.90	$162.90
Purchase #7	$32.63	11.485%	$36.3776	$36.38	$36.40	$36.40
7 purchase totals =	$982.89		$1,085.8247	$1,085.82	$1,085.80	$1,085.90