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	$169.78	12.691%	$191.3268	$191.33	$191.35	$191.30
Purchase #2	$232.40	5.351%	$244.8357	$244.84	$244.85	$244.80
Purchase #3	$47.54	11.265%	$52.8954	$52.90	$52.90	$52.90
Purchase #4	$111.58	4.637%	$116.754	$116.75	$116.75	$116.80
Purchase #5	$56.94	11.503%	$63.4898	$63.49	$63.50	$63.50
Purchase #6	$28.69	11.523%	$31.9959	$32.00	$32.00	$32.00
Purchase #7	$50.37	7.453%	$54.1241	$54.12	$54.10	$54.10
7 purchase totals =	$697.30		$755.4217	$755.43	$755.45	$755.40