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	$46.43	10.636%	$51.3683	$51.37	$51.35	$51.40
Purchase #2	$181.51	7.654%	$195.4028	$195.40	$195.40	$195.40
Purchase #3	$63.35	10.172%	$69.794	$69.79	$69.80	$69.80
Purchase #4	$132.47	13.816%	$150.7721	$150.77	$150.75	$150.80
Purchase #5	$111.81	7.312%	$119.9855	$119.99	$120.00	$120.00
Purchase #6	$113.46	11.835%	$126.888	$126.89	$126.90	$126.90
Purchase #7	$53.52	11.176%	$59.5014	$59.50	$59.50	$59.50
7 purchase totals =	$702.55		$773.7121	$773.71	$773.70	$773.80