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	$100.53	7.512%	$108.0818	$108.08	$108.10	$108.10
Purchase #2	$147.59	10.607%	$163.2449	$163.24	$163.25	$163.20
Purchase #3	$123.35	12.675%	$138.9846	$138.98	$139.00	$139.00
Purchase #4	$41.93	10.455%	$46.3138	$46.31	$46.30	$46.30
Purchase #5	$231.86	10.577%	$256.3838	$256.38	$256.40	$256.40
Purchase #6	$124.69	5.754%	$131.8647	$131.86	$131.85	$131.90
Purchase #7	$221.34	3.702%	$229.534	$229.53	$229.55	$229.50
7 purchase totals =	$991.29		$1,074.4076	$1,074.38	$1,074.45	$1,074.40