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	$232.80	7.506%	$250.274	$250.27	$250.25	$250.30
Purchase #2	$9.73	11.233%	$10.823	$10.82	$10.80	$10.80
Purchase #3	$104.30	11.235%	$116.0181	$116.02	$116.00	$116.00
Purchase #4	$78.62	10.528%	$86.8971	$86.90	$86.90	$86.90
Purchase #5	$161.43	13.845%	$183.78	$183.78	$183.80	$183.80
Purchase #6	$229.78	3.687%	$238.252	$238.25	$238.25	$238.30
Purchase #7	$32.70	11.315%	$36.4	$36.40	$36.40	$36.40
7 purchase totals =	$849.36		$922.4442	$922.44	$922.40	$922.50