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	$237.56	10.351%	$262.1498	$262.15	$262.15	$262.10
Purchase #2	$197.49	12.504%	$222.1841	$222.18	$222.20	$222.20
Purchase #3	$51.50	7.214%	$55.2152	$55.22	$55.20	$55.20
Purchase #4	$136.83	10.520%	$151.2245	$151.22	$151.20	$151.20
Purchase #5	$75.26	3.614%	$77.9799	$77.98	$78.00	$78.00
Purchase #6	$35.62	6.511%	$37.9392	$37.94	$37.95	$37.90
Purchase #7	$86.41	10.660%	$95.6213	$95.62	$95.60	$95.60
7 purchase totals =	$820.67		$902.3140	$902.31	$902.30	$902.20