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	$169.66	10.436%	$187.3657	$187.37	$187.35	$187.40
Purchase #2	$134.59	3.621%	$139.4635	$139.46	$139.45	$139.50
Purchase #3	$79.76	9.539%	$87.3683	$87.37	$87.35	$87.40
Purchase #4	$61.57	3.318%	$63.6129	$63.61	$63.60	$63.60
Purchase #5	$212.45	5.306%	$223.7226	$223.72	$223.70	$223.70
Purchase #6	$105.72	5.761%	$111.8105	$111.81	$111.80	$111.80
Purchase #7	$71.47	4.274%	$74.5246	$74.52	$74.50	$74.50
7 purchase totals =	$835.22		$887.8681	$887.86	$887.75	$887.90