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	$135.46	4.706%	$141.8347	$141.83	$141.85	$141.80
Purchase #2	$171.67	11.189%	$190.8782	$190.88	$190.90	$190.90
Purchase #3	$160.50	12.605%	$180.731	$180.73	$180.75	$180.70
Purchase #4	$47.40	3.483%	$49.0509	$49.05	$49.05	$49.10
Purchase #5	$71.53	7.388%	$76.8146	$76.81	$76.80	$76.80
Purchase #6	$139.29	12.323%	$156.4547	$156.45	$156.45	$156.50
Purchase #7	$236.83	13.454%	$268.6931	$268.69	$268.70	$268.70
7 purchase totals =	$962.68		$1,064.4572	$1,064.44	$1,064.50	$1,064.50