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	$84.81	6.814%	$90.589	$90.59	$90.60	$90.60
Purchase #2	$175.51	6.432%	$186.7988	$186.80	$186.80	$186.80
Purchase #3	$146.25	4.345%	$152.6046	$152.60	$152.60	$152.60
Purchase #4	$204.43	3.204%	$210.9799	$210.98	$211.00	$211.00
Purchase #5	$77.74	11.202%	$86.4484	$86.45	$86.45	$86.40
Purchase #6	$151.56	6.617%	$161.5887	$161.59	$161.60	$161.60
Purchase #7	$136.94	4.582%	$143.2146	$143.21	$143.20	$143.20
7 purchase totals =	$977.24		$1,032.2240	$1,032.22	$1,032.25	$1,032.20