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	$152.40	12.863%	$172.0032	$172.00	$172.00	$172.00
Purchase #2	$167.70	10.632%	$185.5299	$185.53	$185.55	$185.50
Purchase #3	$70.65	11.404%	$78.7069	$78.71	$78.70	$78.70
Purchase #4	$34.47	3.596%	$35.7095	$35.71	$35.70	$35.70
Purchase #5	$126.36	3.614%	$130.9267	$130.93	$130.95	$130.90
Purchase #6	$148.34	9.351%	$162.2113	$162.21	$162.20	$162.20
Purchase #7	$94.25	5.813%	$99.7288	$99.73	$99.75	$99.70
7 purchase totals =	$794.17		$864.8163	$864.82	$864.85	$864.70