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	$81.90	12.498%	$92.1359	$92.14	$92.15	$92.10
Purchase #2	$176.51	11.285%	$196.4292	$196.43	$196.45	$196.40
Purchase #3	$172.93	7.506%	$185.9101	$185.91	$185.90	$185.90
Purchase #4	$124.64	7.680%	$134.2124	$134.21	$134.20	$134.20
Purchase #5	$34.76	3.415%	$35.9471	$35.95	$35.95	$35.90
Purchase #6	$64.42	4.157%	$67.0979	$67.10	$67.10	$67.10
Purchase #7	$5.46	12.176%	$6.1248	$6.12	$6.10	$6.10
7 purchase totals =	$660.62		$717.8574	$717.86	$717.85	$717.70