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	$91.74	4.391%	$95.7683	$95.77	$95.75	$95.80
Purchase #2	$75.69	13.421%	$85.8484	$85.85	$85.85	$85.80
Purchase #3	$79.34	4.330%	$82.7754	$82.78	$82.80	$82.80
Purchase #4	$135.73	9.262%	$148.3013	$148.30	$148.30	$148.30
Purchase #5	$88.53	12.580%	$99.6671	$99.67	$99.65	$99.70
Purchase #6	$183.86	8.567%	$199.6113	$199.61	$199.60	$199.60
Purchase #7	$56.64	5.420%	$59.7099	$59.71	$59.70	$59.70
7 purchase totals =	$711.53		$771.6817	$771.69	$771.65	$771.70