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	$28.87	10.661%	$31.9478	$31.95	$31.95	$31.90
Purchase #2	$49.47	12.724%	$55.7646	$55.76	$55.75	$55.80
Purchase #3	$34.36	10.313%	$37.9035	$37.90	$37.90	$37.90
Purchase #4	$8.44	3.439%	$8.7303	$8.73	$8.75	$8.70
Purchase #5	$248.45	6.710%	$265.121	$265.12	$265.10	$265.10
Purchase #6	$118.35	11.196%	$131.6005	$131.60	$131.60	$131.60
Purchase #7	$157.38	7.696%	$169.492	$169.49	$169.50	$169.50
7 purchase totals =	$645.32		$700.5597	$700.55	$700.55	$700.50