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	$134.95	10.858%	$149.6029	$149.60	$149.60	$149.60
Purchase #2	$98.82	7.221%	$105.9558	$105.96	$105.95	$106.00
Purchase #3	$81.41	9.526%	$89.1651	$89.17	$89.15	$89.20
Purchase #4	$149.31	13.731%	$169.8118	$169.81	$169.80	$169.80
Purchase #5	$226.59	12.501%	$254.916	$254.92	$254.90	$254.90
Purchase #6	$27.48	3.620%	$28.4748	$28.47	$28.45	$28.50
Purchase #7	$150.51	10.730%	$166.6597	$166.66	$166.65	$166.70
7 purchase totals =	$869.07		$964.5861	$964.59	$964.50	$964.70