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	$83.73	5.870%	$88.645	$88.65	$88.65	$88.60
Purchase #2	$55.66	3.287%	$57.4895	$57.49	$57.50	$57.50
Purchase #3	$32.53	6.640%	$34.69	$34.69	$34.70	$34.70
Purchase #4	$88.38	12.308%	$99.2578	$99.26	$99.25	$99.30
Purchase #5	$103.42	5.499%	$109.1071	$109.11	$109.10	$109.10
Purchase #6	$88.44	10.654%	$97.8624	$97.86	$97.85	$97.90
Purchase #7	$194.88	11.838%	$217.9499	$217.95	$217.95	$217.90
7 purchase totals =	$647.04		$705.0017	$705.01	$705.00	$705.00