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	$98.95	13.498%	$112.3063	$112.31	$112.30	$112.30
Purchase #2	$118.64	3.345%	$122.6085	$122.61	$122.60	$122.60
Purchase #3	$100.85	8.609%	$109.5322	$109.53	$109.55	$109.50
Purchase #4	$113.50	10.352%	$125.2495	$125.25	$125.25	$125.20
Purchase #5	$143.48	10.161%	$158.059	$158.06	$158.05	$158.10
Purchase #6	$227.26	10.410%	$250.9178	$250.92	$250.90	$250.90
Purchase #7	$158.63	13.853%	$180.605	$180.61	$180.60	$180.60
7 purchase totals =	$961.31		$1,059.2783	$1,059.29	$1,059.25	$1,059.20