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	$215.45	8.581%	$233.9378	$233.94	$233.95	$233.90
Purchase #2	$138.50	5.425%	$146.0136	$146.01	$146.00	$146.00
Purchase #3	$192.80	13.511%	$218.8492	$218.85	$218.85	$218.80
Purchase #4	$149.67	8.385%	$162.2198	$162.22	$162.20	$162.20
Purchase #5	$208.55	8.589%	$226.4624	$226.46	$226.45	$226.50
Purchase #6	$141.32	6.777%	$150.8973	$150.90	$150.90	$150.90
Purchase #7	$105.53	10.143%	$116.2339	$116.23	$116.25	$116.20
7 purchase totals =	$1,151.82		$1,254.6140	$1,254.61	$1,254.60	$1,254.50