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	$108.29	13.698%	$123.1236	$123.12	$123.10	$123.10
Purchase #2	$241.82	3.780%	$250.9608	$250.96	$250.95	$251.00
Purchase #3	$236.80	3.598%	$245.3201	$245.32	$245.30	$245.30
Purchase #4	$137.98	9.386%	$150.9308	$150.93	$150.95	$150.90
Purchase #5	$5.82	13.223%	$6.5896	$6.59	$6.60	$6.60
Purchase #6	$113.43	5.210%	$119.3397	$119.34	$119.35	$119.30
Purchase #7	$188.55	10.478%	$208.3063	$208.31	$208.30	$208.30
7 purchase totals =	$1,032.69		$1,104.5709	$1,104.57	$1,104.55	$1,104.50