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	$66.61	4.682%	$69.7287	$69.73	$69.75	$69.70
Purchase #2	$78.93	6.206%	$83.8284	$83.83	$83.85	$83.80
Purchase #3	$178.51	7.872%	$192.5623	$192.56	$192.55	$192.60
Purchase #4	$222.56	4.662%	$232.9357	$232.94	$232.95	$232.90
Purchase #5	$89.84	10.782%	$99.5265	$99.53	$99.55	$99.50
Purchase #6	$81.26	12.238%	$91.2046	$91.20	$91.20	$91.20
Purchase #7	$94.76	4.784%	$99.2933	$99.29	$99.30	$99.30
7 purchase totals =	$812.47		$869.0795	$869.08	$869.15	$869.00