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	$101.50	12.121%	$113.8028	$113.80	$113.80	$113.80
Purchase #2	$28.66	11.366%	$31.9175	$31.92	$31.90	$31.90
Purchase #3	$213.85	11.423%	$238.2781	$238.28	$238.30	$238.30
Purchase #4	$211.30	10.489%	$233.4633	$233.46	$233.45	$233.50
Purchase #5	$192.45	6.733%	$205.4077	$205.41	$205.40	$205.40
Purchase #6	$137.86	11.511%	$153.7291	$153.73	$153.75	$153.70
Purchase #7	$69.49	13.244%	$78.6933	$78.69	$78.70	$78.70
7 purchase totals =	$955.11		$1,055.2918	$1,055.29	$1,055.30	$1,055.30