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	$246.39	7.526%	$264.9333	$264.93	$264.95	$264.90
Purchase #2	$140.64	12.842%	$158.701	$158.70	$158.70	$158.70
Purchase #3	$72.64	8.219%	$78.6103	$78.61	$78.60	$78.60
Purchase #4	$231.89	10.430%	$256.0761	$256.08	$256.10	$256.10
Purchase #5	$119.46	3.874%	$124.0879	$124.09	$124.10	$124.10
Purchase #6	$176.28	6.308%	$187.3997	$187.40	$187.40	$187.40
Purchase #7	$92.54	8.297%	$100.218	$100.22	$100.20	$100.20
7 purchase totals =	$1,079.84		$1,170.0263	$1,170.03	$1,170.05	$1,170.00