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	$214.65	5.185%	$225.7796	$225.78	$225.80	$225.80
Purchase #2	$42.90	5.463%	$45.2436	$45.24	$45.25	$45.20
Purchase #3	$106.46	4.764%	$111.5318	$111.53	$111.55	$111.50
Purchase #4	$139.43	11.124%	$154.9402	$154.94	$154.95	$154.90
Purchase #5	$68.70	8.178%	$74.3183	$74.32	$74.30	$74.30
Purchase #6	$88.39	7.861%	$95.3383	$95.34	$95.35	$95.30
Purchase #7	$200.63	8.770%	$218.2253	$218.23	$218.25	$218.20
7 purchase totals =	$861.16		$925.3771	$925.38	$925.45	$925.20