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	$32.56	8.389%	$35.2915	$35.29	$35.30	$35.30
Purchase #2	$145.39	5.566%	$153.4824	$153.48	$153.50	$153.50
Purchase #3	$239.50	10.387%	$264.3769	$264.38	$264.40	$264.40
Purchase #4	$177.32	8.785%	$192.8976	$192.90	$192.90	$192.90
Purchase #5	$97.30	13.578%	$110.5114	$110.51	$110.50	$110.50
Purchase #6	$80.71	10.393%	$89.0982	$89.10	$89.10	$89.10
Purchase #7	$54.39	13.514%	$61.7403	$61.74	$61.75	$61.70
7 purchase totals =	$827.17		$907.3983	$907.40	$907.45	$907.40