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	$200.94	13.836%	$228.7421	$228.74	$228.75	$228.70
Purchase #2	$139.45	10.403%	$153.957	$153.96	$153.95	$154.00
Purchase #3	$100.59	8.362%	$109.0013	$109.00	$109.00	$109.00
Purchase #4	$96.59	7.405%	$103.7425	$103.74	$103.75	$103.70
Purchase #5	$77.38	5.807%	$81.8735	$81.87	$81.85	$81.90
Purchase #6	$200.86	9.675%	$220.2932	$220.29	$220.30	$220.30
Purchase #7	$111.82	10.778%	$123.872	$123.87	$123.85	$123.90
7 purchase totals =	$927.63		$1,021.4816	$1,021.47	$1,021.45	$1,021.50