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	$34.56	8.691%	$37.5636	$37.56	$37.55	$37.60
Purchase #2	$35.73	4.724%	$37.4179	$37.42	$37.40	$37.40
Purchase #3	$12.94	12.465%	$14.553	$14.55	$14.55	$14.60
Purchase #4	$80.25	13.749%	$91.2836	$91.28	$91.30	$91.30
Purchase #5	$208.43	7.535%	$224.1352	$224.14	$224.15	$224.10
Purchase #6	$178.64	11.110%	$198.4869	$198.49	$198.50	$198.50
Purchase #7	$208.27	8.387%	$225.7376	$225.74	$225.75	$225.70
7 purchase totals =	$758.82		$829.1778	$829.18	$829.20	$829.20