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	$101.90	3.620%	$105.5888	$105.59	$105.60	$105.60
Purchase #2	$180.89	4.120%	$188.3427	$188.34	$188.35	$188.30
Purchase #3	$91.86	8.498%	$99.6663	$99.67	$99.65	$99.70
Purchase #4	$78.75	8.468%	$85.4186	$85.42	$85.40	$85.40
Purchase #5	$85.77	5.460%	$90.453	$90.45	$90.45	$90.50
Purchase #6	$225.93	9.234%	$246.7924	$246.79	$246.80	$246.80
Purchase #7	$176.68	13.698%	$200.8816	$200.88	$200.90	$200.90
7 purchase totals =	$941.78		$1,017.1434	$1,017.14	$1,017.15	$1,017.20