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	$65.86	11.107%	$73.1751	$73.18	$73.20	$73.20
Purchase #2	$64.50	3.102%	$66.5008	$66.50	$66.50	$66.50
Purchase #3	$103.28	6.372%	$109.861	$109.86	$109.85	$109.90
Purchase #4	$35.36	13.425%	$40.1071	$40.11	$40.10	$40.10
Purchase #5	$189.35	7.174%	$202.934	$202.93	$202.95	$202.90
Purchase #6	$40.72	6.491%	$43.3631	$43.36	$43.35	$43.40
Purchase #7	$94.40	5.433%	$99.5288	$99.53	$99.55	$99.50
7 purchase totals =	$593.47		$635.4699	$635.47	$635.50	$635.50