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	$86.43	5.325%	$91.0324	$91.03	$91.05	$91.00
Purchase #2	$100.84	7.229%	$108.1297	$108.13	$108.15	$108.10
Purchase #3	$40.30	5.603%	$42.558	$42.56	$42.55	$42.60
Purchase #4	$208.76	7.194%	$223.7782	$223.78	$223.80	$223.80
Purchase #5	$123.28	8.705%	$134.0115	$134.01	$134.00	$134.00
Purchase #6	$138.30	4.306%	$144.2552	$144.26	$144.25	$144.30
Purchase #7	$188.76	13.646%	$214.5182	$214.52	$214.50	$214.50
7 purchase totals =	$886.67		$958.2832	$958.29	$958.30	$958.30