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	$83.31	10.614%	$92.1525	$92.15	$92.15	$92.20
Purchase #2	$244.32	12.201%	$274.1295	$274.13	$274.15	$274.10
Purchase #3	$146.74	5.102%	$154.2267	$154.23	$154.25	$154.20
Purchase #4	$212.58	12.335%	$238.8017	$238.80	$238.80	$238.80
Purchase #5	$154.57	3.856%	$160.5302	$160.53	$160.55	$160.50
Purchase #6	$249.48	12.691%	$281.1415	$281.14	$281.15	$281.10
Purchase #7	$186.39	7.476%	$200.3245	$200.32	$200.30	$200.30
7 purchase totals =	$1,277.39		$1,401.3066	$1,401.30	$1,401.35	$1,401.20