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	$10.51	12.805%	$11.8558	$11.86	$11.85	$11.90
Purchase #2	$67.73	12.700%	$76.3317	$76.33	$76.35	$76.30
Purchase #3	$147.56	8.701%	$160.3992	$160.40	$160.40	$160.40
Purchase #4	$244.81	4.837%	$256.6515	$256.65	$256.65	$256.70
Purchase #5	$42.83	7.186%	$45.9078	$45.91	$45.90	$45.90
Purchase #6	$118.85	9.724%	$130.407	$130.41	$130.40	$130.40
Purchase #7	$203.69	5.816%	$215.5366	$215.54	$215.55	$215.50
7 purchase totals =	$835.98		$897.0896	$897.10	$897.10	$897.10