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	$59.88	13.385%	$67.8949	$67.89	$67.90	$67.90
Purchase #2	$18.58	11.661%	$20.7466	$20.75	$20.75	$20.70
Purchase #3	$48.25	10.741%	$53.4325	$53.43	$53.45	$53.40
Purchase #4	$131.33	3.234%	$135.5772	$135.58	$135.60	$135.60
Purchase #5	$142.48	13.846%	$162.2078	$162.21	$162.20	$162.20
Purchase #6	$32.53	3.598%	$33.7004	$33.70	$33.70	$33.70
Purchase #7	$40.57	7.797%	$43.7332	$43.73	$43.75	$43.70
7 purchase totals =	$473.62		$517.2926	$517.29	$517.35	$517.20