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	$72.53	5.827%	$76.7563	$76.76	$76.75	$76.80
Purchase #2	$218.49	12.524%	$245.8537	$245.85	$245.85	$245.90
Purchase #3	$158.37	13.433%	$179.6438	$179.64	$179.65	$179.60
Purchase #4	$66.67	10.160%	$73.4437	$73.44	$73.45	$73.40
Purchase #5	$136.93	5.415%	$144.3448	$144.34	$144.35	$144.30
Purchase #6	$97.78	6.613%	$104.2462	$104.25	$104.25	$104.20
Purchase #7	$246.77	6.463%	$262.7187	$262.72	$262.70	$262.70
7 purchase totals =	$997.54		$1,087.0072	$1,087.00	$1,087.00	$1,086.90