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	$172.94	12.273%	$194.1649	$194.16	$194.15	$194.20
Purchase #2	$40.38	11.747%	$45.1234	$45.12	$45.10	$45.10
Purchase #3	$180.70	10.413%	$199.5163	$199.52	$199.50	$199.50
Purchase #4	$82.70	9.822%	$90.8228	$90.82	$90.80	$90.80
Purchase #5	$230.47	11.821%	$257.7139	$257.71	$257.70	$257.70
Purchase #6	$12.52	9.869%	$13.7556	$13.76	$13.75	$13.80
Purchase #7	$162.28	11.405%	$180.788	$180.79	$180.80	$180.80
7 purchase totals =	$881.99		$981.8849	$981.88	$981.80	$981.90