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	$116.80	4.423%	$121.9661	$121.97	$121.95	$122.00
Purchase #2	$38.48	10.304%	$42.445	$42.45	$42.45	$42.40
Purchase #3	$71.37	10.137%	$78.6048	$78.60	$78.60	$78.60
Purchase #4	$49.27	11.324%	$54.8493	$54.85	$54.85	$54.80
Purchase #5	$92.82	9.451%	$101.5924	$101.59	$101.60	$101.60
Purchase #6	$130.58	12.690%	$147.1506	$147.15	$147.15	$147.20
Purchase #7	$190.64	9.457%	$208.6688	$208.67	$208.65	$208.70
7 purchase totals =	$689.96		$755.2770	$755.28	$755.25	$755.30