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	$69.34	12.715%	$78.1566	$78.16	$78.15	$78.20
Purchase #2	$114.70	4.521%	$119.8856	$119.89	$119.90	$119.90
Purchase #3	$207.77	9.633%	$227.7845	$227.78	$227.80	$227.80
Purchase #4	$167.73	4.694%	$175.6032	$175.60	$175.60	$175.60
Purchase #5	$232.80	5.633%	$245.9136	$245.91	$245.90	$245.90
Purchase #6	$210.46	8.367%	$228.0692	$228.07	$228.05	$228.10
Purchase #7	$9.89	7.138%	$10.5959	$10.60	$10.60	$10.60
7 purchase totals =	$1,012.69		$1,086.0086	$1,086.01	$1,086.00	$1,086.10