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	$96.28	4.806%	$100.9072	$100.91	$100.90	$100.90
Purchase #2	$101.86	11.286%	$113.3559	$113.36	$113.35	$113.40
Purchase #3	$180.72	9.867%	$198.5516	$198.55	$198.55	$198.60
Purchase #4	$27.55	7.325%	$29.568	$29.57	$29.55	$29.60
Purchase #5	$85.89	10.799%	$95.1653	$95.17	$95.15	$95.20
Purchase #6	$128.82	13.345%	$146.011	$146.01	$146.00	$146.00
Purchase #7	$198.29	10.380%	$218.8725	$218.87	$218.85	$218.90
7 purchase totals =	$819.41		$902.4315	$902.44	$902.35	$902.60