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	$143.25	6.282%	$152.249	$152.25	$152.25	$152.20
Purchase #2	$113.56	12.241%	$127.4609	$127.46	$127.45	$127.50
Purchase #3	$209.43	3.607%	$216.9841	$216.98	$217.00	$217.00
Purchase #4	$243.59	12.413%	$273.8268	$273.83	$273.85	$273.80
Purchase #5	$107.65	10.182%	$118.6109	$118.61	$118.60	$118.60
Purchase #6	$60.83	5.701%	$64.2979	$64.30	$64.30	$64.30
Purchase #7	$78.56	11.667%	$87.7256	$87.73	$87.75	$87.70
7 purchase totals =	$956.87		$1,041.1552	$1,041.16	$1,041.20	$1,041.10