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	$64.56	11.179%	$71.7772	$71.78	$71.80	$71.80
Purchase #2	$24.53	12.135%	$27.5067	$27.51	$27.50	$27.50
Purchase #3	$32.81	7.402%	$35.2386	$35.24	$35.25	$35.20
Purchase #4	$121.90	4.532%	$127.4245	$127.42	$127.40	$127.40
Purchase #5	$152.34	10.745%	$168.7089	$168.71	$168.70	$168.70
Purchase #6	$143.32	7.624%	$154.2467	$154.25	$154.25	$154.20
Purchase #7	$172.38	9.864%	$189.3836	$189.38	$189.40	$189.40
7 purchase totals =	$711.84		$774.2862	$774.29	$774.30	$774.20