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	$174.88	12.435%	$196.6263	$196.63	$196.65	$196.60
Purchase #2	$162.31	7.168%	$173.9444	$173.94	$173.95	$173.90
Purchase #3	$45.88	12.756%	$51.7325	$51.73	$51.75	$51.70
Purchase #4	$163.65	11.735%	$182.8543	$182.85	$182.85	$182.90
Purchase #5	$181.27	4.401%	$189.2477	$189.25	$189.25	$189.20
Purchase #6	$78.93	4.266%	$82.2972	$82.30	$82.30	$82.30
Purchase #7	$108.99	13.786%	$124.0154	$124.02	$124.00	$124.00
7 purchase totals =	$915.91		$1,000.7178	$1,000.72	$1,000.75	$1,000.60