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	$106.84	13.205%	$120.9482	$120.95	$120.95	$120.90
Purchase #2	$85.48	10.472%	$94.4315	$94.43	$94.45	$94.40
Purchase #3	$29.45	13.686%	$33.4805	$33.48	$33.50	$33.50
Purchase #4	$185.72	9.396%	$203.1703	$203.17	$203.15	$203.20
Purchase #5	$61.88	11.646%	$69.0865	$69.09	$69.10	$69.10
Purchase #6	$149.72	10.137%	$164.8971	$164.90	$164.90	$164.90
Purchase #7	$89.35	11.606%	$99.72	$99.72	$99.70	$99.70
7 purchase totals =	$708.44		$785.7341	$785.74	$785.75	$785.70