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	$113.86	8.698%	$123.7635	$123.76	$123.75	$123.80
Purchase #2	$98.60	3.110%	$101.6665	$101.67	$101.65	$101.70
Purchase #3	$156.25	11.453%	$174.1453	$174.15	$174.15	$174.10
Purchase #4	$246.49	5.827%	$260.853	$260.85	$260.85	$260.90
Purchase #5	$96.43	6.733%	$102.9226	$102.92	$102.90	$102.90
Purchase #6	$174.71	12.199%	$196.0229	$196.02	$196.00	$196.00
Purchase #7	$144.70	13.412%	$164.1072	$164.11	$164.10	$164.10
7 purchase totals =	$1,031.04		$1,123.4810	$1,123.48	$1,123.40	$1,123.50