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	$102.79	6.277%	$109.2421	$109.24	$109.25	$109.20
Purchase #2	$65.82	11.348%	$73.2893	$73.29	$73.30	$73.30
Purchase #3	$74.87	9.581%	$82.0433	$82.04	$82.05	$82.00
Purchase #4	$81.89	10.813%	$90.7448	$90.74	$90.75	$90.70
Purchase #5	$90.99	8.566%	$98.7842	$98.78	$98.80	$98.80
Purchase #6	$69.63	12.208%	$78.1304	$78.13	$78.15	$78.10
Purchase #7	$192.26	7.168%	$206.0412	$206.04	$206.05	$206.00
7 purchase totals =	$678.25		$738.2753	$738.26	$738.35	$738.10