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	$200.59	9.375%	$219.3953	$219.40	$219.40	$219.40
Purchase #2	$140.30	11.484%	$156.4121	$156.41	$156.40	$156.40
Purchase #3	$147.63	6.483%	$157.2009	$157.20	$157.20	$157.20
Purchase #4	$12.56	6.779%	$13.4114	$13.41	$13.40	$13.40
Purchase #5	$208.71	9.407%	$228.3433	$228.34	$228.35	$228.30
Purchase #6	$106.51	9.331%	$116.4484	$116.45	$116.45	$116.40
Purchase #7	$146.83	12.642%	$165.3922	$165.39	$165.40	$165.40
7 purchase totals =	$963.13		$1,056.6036	$1,056.60	$1,056.60	$1,056.50