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	$191.44	6.250%	$203.405	$203.41	$203.40	$203.40
Purchase #2	$37.29	13.387%	$42.282	$42.28	$42.30	$42.30
Purchase #3	$83.70	7.258%	$89.7749	$89.77	$89.75	$89.80
Purchase #4	$28.32	3.238%	$29.237	$29.24	$29.25	$29.20
Purchase #5	$167.90	13.624%	$190.7747	$190.77	$190.75	$190.80
Purchase #6	$150.43	4.561%	$157.2911	$157.29	$157.30	$157.30
Purchase #7	$171.60	7.570%	$184.5901	$184.59	$184.60	$184.60
7 purchase totals =	$830.68		$897.3548	$897.35	$897.35	$897.40