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	$130.32	7.749%	$140.4185	$140.42	$140.40	$140.40
Purchase #2	$183.42	13.718%	$208.5816	$208.58	$208.60	$208.60
Purchase #3	$242.91	10.784%	$269.1054	$269.11	$269.10	$269.10
Purchase #4	$35.71	4.357%	$37.2659	$37.27	$37.25	$37.30
Purchase #5	$210.60	3.454%	$217.8741	$217.87	$217.85	$217.90
Purchase #6	$99.27	5.874%	$105.1011	$105.10	$105.10	$105.10
Purchase #7	$120.81	13.747%	$137.4178	$137.42	$137.40	$137.40
7 purchase totals =	$1,023.04		$1,115.7644	$1,115.77	$1,115.70	$1,115.80