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	$192.50	6.452%	$204.9201	$204.92	$204.90	$204.90
Purchase #2	$173.82	10.174%	$191.5044	$191.50	$191.50	$191.50
Purchase #3	$137.56	3.594%	$142.5039	$142.50	$142.50	$142.50
Purchase #4	$144.41	8.813%	$157.1369	$157.14	$157.15	$157.10
Purchase #5	$71.29	8.310%	$77.2142	$77.21	$77.20	$77.20
Purchase #6	$83.68	3.308%	$86.4481	$86.45	$86.45	$86.40
Purchase #7	$64.87	10.336%	$71.575	$71.58	$71.60	$71.60
7 purchase totals =	$868.13		$931.3026	$931.30	$931.30	$931.20