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	$164.94	4.769%	$172.806	$172.81	$172.80	$172.80
Purchase #2	$214.26	12.427%	$240.8861	$240.89	$240.90	$240.90
Purchase #3	$140.81	13.260%	$159.4814	$159.48	$159.50	$159.50
Purchase #4	$90.79	13.478%	$103.0267	$103.03	$103.05	$103.00
Purchase #5	$181.70	6.528%	$193.5614	$193.56	$193.55	$193.60
Purchase #6	$138.37	13.783%	$157.4415	$157.44	$157.45	$157.40
Purchase #7	$86.90	10.595%	$96.1071	$96.11	$96.10	$96.10
7 purchase totals =	$1,017.77		$1,123.3102	$1,123.32	$1,123.35	$1,123.30