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	$82.47	8.750%	$89.6861	$89.69	$89.70	$89.70
Purchase #2	$123.46	6.619%	$131.6318	$131.63	$131.65	$131.60
Purchase #3	$78.77	9.162%	$85.9869	$85.99	$86.00	$86.00
Purchase #4	$197.75	7.532%	$212.6445	$212.64	$212.65	$212.60
Purchase #5	$29.94	5.223%	$31.5038	$31.50	$31.50	$31.50
Purchase #6	$119.46	9.438%	$130.7346	$130.73	$130.75	$130.70
Purchase #7	$79.61	8.852%	$86.6571	$86.66	$86.65	$86.70
7 purchase totals =	$711.46		$768.8448	$768.84	$768.90	$768.80