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	$95.41	9.624%	$104.5923	$104.59	$104.60	$104.60
Purchase #2	$108.36	13.611%	$123.1089	$123.11	$123.10	$123.10
Purchase #3	$208.52	7.232%	$223.6002	$223.60	$223.60	$223.60
Purchase #4	$139.27	13.524%	$158.1049	$158.10	$158.10	$158.10
Purchase #5	$115.58	11.305%	$128.6463	$128.65	$128.65	$128.60
Purchase #6	$39.43	3.813%	$40.9335	$40.93	$40.95	$40.90
Purchase #7	$99.51	9.230%	$108.6948	$108.69	$108.70	$108.70
7 purchase totals =	$806.08		$887.6809	$887.67	$887.70	$887.60