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	$134.86	10.495%	$149.0136	$149.01	$149.00	$149.00
Purchase #2	$130.98	6.353%	$139.3012	$139.30	$139.30	$139.30
Purchase #3	$137.90	13.245%	$156.1649	$156.16	$156.15	$156.20
Purchase #4	$55.59	7.606%	$59.8182	$59.82	$59.80	$59.80
Purchase #5	$153.98	10.510%	$170.1633	$170.16	$170.15	$170.20
Purchase #6	$171.67	5.176%	$180.5556	$180.56	$180.55	$180.60
Purchase #7	$45.80	6.331%	$48.6996	$48.70	$48.70	$48.70
7 purchase totals =	$830.78		$903.7164	$903.71	$903.65	$903.80