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	$124.83	12.488%	$140.4188	$140.42	$140.40	$140.40
Purchase #2	$135.31	11.682%	$151.1169	$151.12	$151.10	$151.10
Purchase #3	$96.85	3.637%	$100.3724	$100.37	$100.35	$100.40
Purchase #4	$32.71	7.555%	$35.1812	$35.18	$35.20	$35.20
Purchase #5	$31.80	10.812%	$35.2382	$35.24	$35.25	$35.20
Purchase #6	$53.50	11.588%	$59.6996	$59.70	$59.70	$59.70
Purchase #7	$141.41	8.769%	$153.8102	$153.81	$153.80	$153.80
7 purchase totals =	$616.41		$675.8373	$675.84	$675.80	$675.80