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	$145.56	6.802%	$155.461	$155.46	$155.45	$155.50
Purchase #2	$37.51	3.211%	$38.7144	$38.71	$38.70	$38.70
Purchase #3	$136.78	11.396%	$152.3674	$152.37	$152.35	$152.40
Purchase #4	$32.94	10.282%	$36.3269	$36.33	$36.35	$36.30
Purchase #5	$232.34	4.405%	$242.5746	$242.57	$242.55	$242.60
Purchase #6	$150.79	5.324%	$158.8181	$158.82	$158.80	$158.80
Purchase #7	$143.25	9.488%	$156.8416	$156.84	$156.85	$156.80
7 purchase totals =	$879.17		$941.1040	$941.10	$941.05	$941.10