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	$187.85	6.597%	$200.2425	$200.24	$200.25	$200.20
Purchase #2	$26.78	10.439%	$29.5756	$29.58	$29.60	$29.60
Purchase #3	$70.31	3.244%	$72.5909	$72.59	$72.60	$72.60
Purchase #4	$14.90	7.130%	$15.9624	$15.96	$15.95	$16.00
Purchase #5	$145.70	12.724%	$164.2389	$164.24	$164.25	$164.20
Purchase #6	$72.76	4.668%	$76.1564	$76.16	$76.15	$76.20
Purchase #7	$154.88	9.687%	$169.8832	$169.88	$169.90	$169.90
7 purchase totals =	$673.18		$728.6499	$728.65	$728.70	$728.70