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	$191.40	13.800%	$217.8132	$217.81	$217.80	$217.80
Purchase #2	$161.25	7.371%	$173.1357	$173.14	$173.15	$173.10
Purchase #3	$69.53	12.740%	$78.3881	$78.39	$78.40	$78.40
Purchase #4	$24.39	5.179%	$25.6532	$25.65	$25.65	$25.70
Purchase #5	$177.98	12.844%	$200.8398	$200.84	$200.85	$200.80
Purchase #6	$44.80	4.656%	$46.8859	$46.89	$46.90	$46.90
Purchase #7	$127.72	9.805%	$140.2429	$140.24	$140.25	$140.20
7 purchase totals =	$797.07		$882.9588	$882.96	$883.00	$882.90