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	$125.87	12.492%	$141.5937	$141.59	$141.60	$141.60
Purchase #2	$211.28	12.777%	$238.2752	$238.28	$238.30	$238.30
Purchase #3	$30.93	8.112%	$33.439	$33.44	$33.45	$33.40
Purchase #4	$233.82	11.525%	$260.7678	$260.77	$260.75	$260.80
Purchase #5	$116.54	10.359%	$128.6124	$128.61	$128.60	$128.60
Purchase #6	$135.75	6.542%	$144.6308	$144.63	$144.65	$144.60
Purchase #7	$59.42	13.570%	$67.4833	$67.48	$67.50	$67.50
7 purchase totals =	$913.61		$1,014.8022	$1,014.80	$1,014.85	$1,014.80