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	$104.46	7.133%	$111.9111	$111.91	$111.90	$111.90
Purchase #2	$99.42	9.659%	$109.023	$109.02	$109.00	$109.00
Purchase #3	$98.79	12.733%	$111.3689	$111.37	$111.35	$111.40
Purchase #4	$220.80	3.636%	$228.8283	$228.83	$228.85	$228.80
Purchase #5	$137.99	5.277%	$145.2717	$145.27	$145.25	$145.30
Purchase #6	$95.45	6.187%	$101.3555	$101.36	$101.35	$101.40
Purchase #7	$189.29	12.658%	$213.2503	$213.25	$213.25	$213.30
7 purchase totals =	$946.20		$1,021.0088	$1,021.01	$1,020.95	$1,021.10