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	$146.64	9.515%	$160.5928	$160.59	$160.60	$160.60
Purchase #2	$76.33	12.138%	$85.5949	$85.59	$85.60	$85.60
Purchase #3	$28.74	8.589%	$31.2085	$31.21	$31.20	$31.20
Purchase #4	$95.65	8.133%	$103.4292	$103.43	$103.45	$103.40
Purchase #5	$160.35	7.264%	$171.9978	$172.00	$172.00	$172.00
Purchase #6	$154.46	11.531%	$172.2708	$172.27	$172.25	$172.30
Purchase #7	$182.96	8.589%	$198.6744	$198.67	$198.65	$198.70
7 purchase totals =	$845.13		$923.7684	$923.76	$923.75	$923.80