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	$80.98	5.861%	$85.7262	$85.73	$85.75	$85.70
Purchase #2	$163.36	12.121%	$183.1609	$183.16	$183.15	$183.20
Purchase #3	$24.89	11.279%	$27.6973	$27.70	$27.70	$27.70
Purchase #4	$247.33	13.741%	$281.3156	$281.32	$281.30	$281.30
Purchase #5	$120.92	5.778%	$127.9068	$127.91	$127.90	$127.90
Purchase #6	$169.97	11.733%	$189.9126	$189.91	$189.90	$189.90
Purchase #7	$153.89	6.732%	$164.2499	$164.25	$164.25	$164.20
7 purchase totals =	$961.34		$1,059.9693	$1,059.98	$1,059.95	$1,059.90