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	$32.25	6.689%	$34.4072	$34.41	$34.40	$34.40
Purchase #2	$182.31	4.431%	$190.3882	$190.39	$190.40	$190.40
Purchase #3	$66.31	7.754%	$71.4517	$71.45	$71.45	$71.50
Purchase #4	$133.43	3.319%	$137.8585	$137.86	$137.85	$137.90
Purchase #5	$112.82	5.234%	$118.725	$118.73	$118.75	$118.70
Purchase #6	$159.44	12.859%	$179.9424	$179.94	$179.95	$179.90
Purchase #7	$22.74	11.261%	$25.3008	$25.30	$25.30	$25.30
7 purchase totals =	$709.30		$758.0738	$758.08	$758.10	$758.10