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	$99.39	13.701%	$113.0074	$113.01	$113.00	$113.00
Purchase #2	$228.55	12.379%	$256.8422	$256.84	$256.85	$256.80
Purchase #3	$177.69	8.467%	$192.735	$192.74	$192.75	$192.70
Purchase #4	$82.71	9.464%	$90.5377	$90.54	$90.55	$90.50
Purchase #5	$197.66	12.488%	$222.3438	$222.34	$222.35	$222.30
Purchase #6	$172.87	6.147%	$183.4963	$183.50	$183.50	$183.50
Purchase #7	$118.85	7.644%	$127.9349	$127.93	$127.95	$127.90
7 purchase totals =	$1,077.72		$1,186.8973	$1,186.90	$1,186.95	$1,186.70