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	$217.95	4.310%	$227.3436	$227.34	$227.35	$227.30
Purchase #2	$128.76	9.825%	$141.4107	$141.41	$141.40	$141.40
Purchase #3	$50.31	11.575%	$56.1334	$56.13	$56.15	$56.10
Purchase #4	$79.30	5.357%	$83.5481	$83.55	$83.55	$83.50
Purchase #5	$79.86	12.677%	$89.9839	$89.98	$90.00	$90.00
Purchase #6	$212.42	7.384%	$228.1051	$228.11	$228.10	$228.10
Purchase #7	$228.79	10.588%	$253.0143	$253.01	$253.00	$253.00
7 purchase totals =	$997.39		$1,079.5391	$1,079.53	$1,079.55	$1,079.40