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	$210.41	3.855%	$218.5213	$218.52	$218.50	$218.50
Purchase #2	$143.69	4.473%	$150.1173	$150.12	$150.10	$150.10
Purchase #3	$188.37	11.190%	$209.4486	$209.45	$209.45	$209.40
Purchase #4	$31.43	5.516%	$33.1637	$33.16	$33.15	$33.20
Purchase #5	$50.91	13.818%	$57.9447	$57.94	$57.95	$57.90
Purchase #6	$97.43	5.603%	$102.889	$102.89	$102.90	$102.90
Purchase #7	$224.99	10.161%	$247.8512	$247.85	$247.85	$247.90
7 purchase totals =	$947.23		$1,019.9358	$1,019.93	$1,019.90	$1,019.90