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	$132.28	6.150%	$140.4152	$140.42	$140.40	$140.40
Purchase #2	$34.81	7.753%	$37.5088	$37.51	$37.50	$37.50
Purchase #3	$84.53	8.327%	$91.5688	$91.57	$91.55	$91.60
Purchase #4	$134.69	6.195%	$143.034	$143.03	$143.05	$143.00
Purchase #5	$44.31	6.710%	$47.2832	$47.28	$47.30	$47.30
Purchase #6	$112.40	6.153%	$119.316	$119.32	$119.30	$119.30
Purchase #7	$196.87	3.380%	$203.5242	$203.52	$203.50	$203.50
7 purchase totals =	$739.89		$782.6502	$782.65	$782.60	$782.60