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	$181.44	10.532%	$200.5493	$200.55	$200.55	$200.50
Purchase #2	$52.38	12.792%	$59.0804	$59.08	$59.10	$59.10
Purchase #3	$62.63	5.833%	$66.2832	$66.28	$66.30	$66.30
Purchase #4	$246.93	9.373%	$270.0747	$270.07	$270.05	$270.10
Purchase #5	$175.76	11.718%	$196.3556	$196.36	$196.35	$196.40
Purchase #6	$135.90	13.589%	$154.3675	$154.37	$154.35	$154.40
Purchase #7	$143.44	4.343%	$149.6696	$149.67	$149.65	$149.70
7 purchase totals =	$998.48		$1,096.3803	$1,096.38	$1,096.35	$1,096.50