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	$97.77	12.168%	$109.6667	$109.67	$109.65	$109.70
Purchase #2	$140.64	10.365%	$155.2173	$155.22	$155.20	$155.20
Purchase #3	$148.89	13.266%	$168.6417	$168.64	$168.65	$168.60
Purchase #4	$227.70	7.603%	$245.012	$245.01	$245.00	$245.00
Purchase #5	$91.92	13.326%	$104.1693	$104.17	$104.15	$104.20
Purchase #6	$127.40	8.117%	$137.7411	$137.74	$137.75	$137.70
Purchase #7	$215.31	3.781%	$223.4509	$223.45	$223.45	$223.50
7 purchase totals =	$1,049.63		$1,143.8990	$1,143.90	$1,143.85	$1,143.90