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	$69.66	5.382%	$73.4091	$73.41	$73.40	$73.40
Purchase #2	$59.27	7.107%	$63.4823	$63.48	$63.50	$63.50
Purchase #3	$119.34	12.756%	$134.563	$134.56	$134.55	$134.60
Purchase #4	$69.39	13.244%	$78.58	$78.58	$78.60	$78.60
Purchase #5	$47.73	7.543%	$51.3303	$51.33	$51.35	$51.30
Purchase #6	$218.65	3.175%	$225.5921	$225.59	$225.60	$225.60
Purchase #7	$241.48	5.781%	$255.44	$255.44	$255.45	$255.40
7 purchase totals =	$825.52		$882.3968	$882.39	$882.45	$882.40