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	$78.66	13.505%	$89.283	$89.28	$89.30	$89.30
Purchase #2	$10.58	6.676%	$11.2863	$11.29	$11.30	$11.30
Purchase #3	$90.53	4.685%	$94.7713	$94.77	$94.75	$94.80
Purchase #4	$29.96	6.477%	$31.9005	$31.90	$31.90	$31.90
Purchase #5	$38.70	13.314%	$43.8525	$43.85	$43.85	$43.90
Purchase #6	$115.54	8.482%	$125.3401	$125.34	$125.35	$125.30
Purchase #7	$199.83	9.612%	$219.0377	$219.04	$219.05	$219.00
7 purchase totals =	$563.80		$615.4714	$615.47	$615.50	$615.50