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	$137.98	13.490%	$156.5935	$156.59	$156.60	$156.60
Purchase #2	$122.86	6.257%	$130.5474	$130.55	$130.55	$130.50
Purchase #3	$239.34	6.797%	$255.6079	$255.61	$255.60	$255.60
Purchase #4	$204.86	8.377%	$222.0211	$222.02	$222.00	$222.00
Purchase #5	$109.75	8.812%	$119.4212	$119.42	$119.40	$119.40
Purchase #6	$54.80	12.181%	$61.4752	$61.48	$61.50	$61.50
Purchase #7	$72.46	10.546%	$80.1016	$80.10	$80.10	$80.10
7 purchase totals =	$942.05		$1,025.7679	$1,025.77	$1,025.75	$1,025.70