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	$224.73	9.640%	$246.394	$246.39	$246.40	$246.40
Purchase #2	$109.98	3.144%	$113.4378	$113.44	$113.45	$113.40
Purchase #3	$134.78	6.470%	$143.5003	$143.50	$143.50	$143.50
Purchase #4	$77.36	4.569%	$80.8946	$80.89	$80.90	$80.90
Purchase #5	$122.90	10.181%	$135.4124	$135.41	$135.40	$135.40
Purchase #6	$104.40	4.649%	$109.2536	$109.25	$109.25	$109.30
Purchase #7	$189.90	3.372%	$196.3034	$196.30	$196.30	$196.30
7 purchase totals =	$964.05		$1,025.1961	$1,025.18	$1,025.20	$1,025.20