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	$51.59	5.503%	$54.429	$54.43	$54.45	$54.40
Purchase #2	$179.89	10.293%	$198.4061	$198.41	$198.40	$198.40
Purchase #3	$238.99	9.768%	$262.3345	$262.33	$262.35	$262.30
Purchase #4	$183.87	10.187%	$202.6008	$202.60	$202.60	$202.60
Purchase #5	$238.84	8.236%	$258.5109	$258.51	$258.50	$258.50
Purchase #6	$95.79	4.205%	$99.818	$99.82	$99.80	$99.80
Purchase #7	$131.26	4.294%	$136.8963	$136.90	$136.90	$136.90
7 purchase totals =	$1,120.23		$1,212.9956	$1,213.00	$1,213.00	$1,212.90