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	$131.31	10.786%	$145.4731	$145.47	$145.45	$145.50
Purchase #2	$48.59	5.324%	$51.1769	$51.18	$51.20	$51.20
Purchase #3	$40.47	10.313%	$44.6437	$44.64	$44.65	$44.60
Purchase #4	$59.72	3.653%	$61.9016	$61.90	$61.90	$61.90
Purchase #5	$160.34	6.669%	$171.0331	$171.03	$171.05	$171.00
Purchase #6	$151.55	8.740%	$164.7955	$164.80	$164.80	$164.80
Purchase #7	$237.77	10.869%	$263.6132	$263.61	$263.60	$263.60
7 purchase totals =	$829.75		$902.6371	$902.63	$902.65	$902.60