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	$112.85	5.707%	$119.2903	$119.29	$119.30	$119.30
Purchase #2	$65.94	10.371%	$72.7786	$72.78	$72.80	$72.80
Purchase #3	$103.96	9.387%	$113.7187	$113.72	$113.70	$113.70
Purchase #4	$154.42	3.703%	$160.1382	$160.14	$160.15	$160.10
Purchase #5	$75.34	13.455%	$85.477	$85.48	$85.50	$85.50
Purchase #6	$80.29	13.374%	$91.028	$91.03	$91.05	$91.00
Purchase #7	$209.52	4.448%	$218.8394	$218.84	$218.85	$218.80
7 purchase totals =	$802.32		$861.2702	$861.28	$861.35	$861.20