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	$87.82	11.603%	$98.0098	$98.01	$98.00	$98.00
Purchase #2	$212.91	9.859%	$233.9008	$233.90	$233.90	$233.90
Purchase #3	$206.93	10.773%	$229.2226	$229.22	$229.20	$229.20
Purchase #4	$135.97	12.116%	$152.4441	$152.44	$152.45	$152.40
Purchase #5	$35.53	11.294%	$39.5428	$39.54	$39.55	$39.50
Purchase #6	$35.39	7.653%	$38.0984	$38.10	$38.10	$38.10
Purchase #7	$40.26	12.677%	$45.3638	$45.36	$45.35	$45.40
7 purchase totals =	$754.81		$836.5823	$836.57	$836.55	$836.50