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	$136.62	5.102%	$143.5904	$143.59	$143.60	$143.60
Purchase #2	$131.70	4.474%	$137.5923	$137.59	$137.60	$137.60
Purchase #3	$78.70	5.793%	$83.2591	$83.26	$83.25	$83.30
Purchase #4	$93.29	7.518%	$100.3035	$100.30	$100.30	$100.30
Purchase #5	$234.61	4.400%	$244.9328	$244.93	$244.95	$244.90
Purchase #6	$124.70	3.869%	$129.5246	$129.52	$129.50	$129.50
Purchase #7	$143.45	8.460%	$155.5859	$155.59	$155.60	$155.60
7 purchase totals =	$943.07		$994.7886	$994.78	$994.80	$994.80