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	$34.53	3.450%	$35.7213	$35.72	$35.70	$35.70
Purchase #2	$67.33	13.634%	$76.5098	$76.51	$76.50	$76.50
Purchase #3	$155.91	4.254%	$162.5424	$162.54	$162.55	$162.50
Purchase #4	$127.95	6.492%	$136.2565	$136.26	$136.25	$136.30
Purchase #5	$77.63	7.142%	$83.1743	$83.17	$83.15	$83.20
Purchase #6	$60.36	5.714%	$63.809	$63.81	$63.80	$63.80
Purchase #7	$62.92	13.351%	$71.3204	$71.32	$71.30	$71.30
7 purchase totals =	$586.63		$629.3337	$629.33	$629.25	$629.30