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	$192.59	9.796%	$211.4561	$211.46	$211.45	$211.50
Purchase #2	$34.51	3.629%	$35.7624	$35.76	$35.75	$35.80
Purchase #3	$140.27	7.582%	$150.9053	$150.91	$150.90	$150.90
Purchase #4	$87.92	3.433%	$90.9383	$90.94	$90.95	$90.90
Purchase #5	$52.84	8.757%	$57.4672	$57.47	$57.45	$57.50
Purchase #6	$40.98	5.757%	$43.3392	$43.34	$43.35	$43.30
Purchase #7	$32.26	8.132%	$34.8834	$34.88	$34.90	$34.90
7 purchase totals =	$581.37		$624.7519	$624.76	$624.75	$624.80