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	$43.82	3.189%	$45.2174	$45.22	$45.20	$45.20
Purchase #2	$127.75	4.291%	$133.2318	$133.23	$133.25	$133.20
Purchase #3	$157.41	9.868%	$172.9432	$172.94	$172.95	$172.90
Purchase #4	$130.75	7.854%	$141.0191	$141.02	$141.00	$141.00
Purchase #5	$35.55	5.465%	$37.4928	$37.49	$37.50	$37.50
Purchase #6	$93.33	10.522%	$103.1502	$103.15	$103.15	$103.20
Purchase #7	$59.88	7.354%	$64.2836	$64.28	$64.30	$64.30
7 purchase totals =	$648.49		$697.3381	$697.33	$697.35	$697.30