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	$32.66	13.376%	$37.0286	$37.03	$37.05	$37.00
Purchase #2	$6.48	11.529%	$7.2271	$7.23	$7.25	$7.20
Purchase #3	$183.63	6.803%	$196.1223	$196.12	$196.10	$196.10
Purchase #4	$238.50	8.769%	$259.4141	$259.41	$259.40	$259.40
Purchase #5	$126.95	12.709%	$143.0841	$143.08	$143.10	$143.10
Purchase #6	$11.65	7.638%	$12.5398	$12.54	$12.55	$12.50
Purchase #7	$209.25	5.368%	$220.4825	$220.48	$220.50	$220.50
7 purchase totals =	$809.12		$875.8985	$875.89	$875.95	$875.80