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	$97.90	6.715%	$104.474	$104.47	$104.45	$104.50
Purchase #2	$134.71	4.481%	$140.7464	$140.75	$140.75	$140.70
Purchase #3	$6.80	7.145%	$7.2859	$7.29	$7.30	$7.30
Purchase #4	$109.43	8.327%	$118.5422	$118.54	$118.55	$118.50
Purchase #5	$184.29	11.596%	$205.6603	$205.66	$205.65	$205.70
Purchase #6	$57.58	3.393%	$59.5337	$59.53	$59.55	$59.50
Purchase #7	$236.52	13.407%	$268.2302	$268.23	$268.25	$268.20
7 purchase totals =	$827.23		$904.4727	$904.47	$904.50	$904.40