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	$96.48	6.871%	$103.1091	$103.11	$103.10	$103.10
Purchase #2	$48.57	7.718%	$52.3186	$52.32	$52.30	$52.30
Purchase #3	$191.34	13.123%	$216.4495	$216.45	$216.45	$216.40
Purchase #4	$247.33	11.613%	$276.0524	$276.05	$276.05	$276.10
Purchase #5	$162.94	5.822%	$172.4264	$172.43	$172.45	$172.40
Purchase #6	$129.86	10.143%	$143.0317	$143.03	$143.05	$143.00
Purchase #7	$246.95	5.361%	$260.189	$260.19	$260.20	$260.20
7 purchase totals =	$1,123.47		$1,223.5767	$1,223.58	$1,223.60	$1,223.50