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	$55.45	12.570%	$62.4201	$62.42	$62.40	$62.40
Purchase #2	$209.53	4.363%	$218.6718	$218.67	$218.65	$218.70
Purchase #3	$9.52	13.279%	$10.7842	$10.78	$10.80	$10.80
Purchase #4	$78.70	8.564%	$85.4399	$85.44	$85.45	$85.40
Purchase #5	$49.99	7.385%	$53.6818	$53.68	$53.70	$53.70
Purchase #6	$100.83	4.805%	$105.6749	$105.67	$105.65	$105.70
Purchase #7	$82.42	11.175%	$91.6304	$91.63	$91.65	$91.60
7 purchase totals =	$586.44		$628.3031	$628.29	$628.30	$628.30