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	$88.77	10.691%	$98.2604	$98.26	$98.25	$98.30
Purchase #2	$82.34	3.277%	$85.0383	$85.04	$85.05	$85.00
Purchase #3	$23.79	8.554%	$25.825	$25.83	$25.85	$25.80
Purchase #4	$41.79	11.376%	$46.544	$46.54	$46.55	$46.50
Purchase #5	$72.93	8.496%	$79.1261	$79.13	$79.15	$79.10
Purchase #6	$65.48	8.267%	$70.8932	$70.89	$70.90	$70.90
Purchase #7	$85.72	4.197%	$89.3177	$89.32	$89.30	$89.30
7 purchase totals =	$460.82		$495.0047	$495.01	$495.05	$494.90