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	$62.30	4.796%	$65.2879	$65.29	$65.30	$65.30
Purchase #2	$216.56	9.219%	$236.5247	$236.52	$236.50	$236.50
Purchase #3	$156.85	5.651%	$165.7136	$165.71	$165.70	$165.70
Purchase #4	$26.53	12.661%	$29.889	$29.89	$29.90	$29.90
Purchase #5	$135.93	3.325%	$140.4497	$140.45	$140.45	$140.40
Purchase #6	$126.77	10.797%	$140.4574	$140.46	$140.45	$140.50
Purchase #7	$215.27	8.237%	$233.0018	$233.00	$233.00	$233.00
7 purchase totals =	$940.21		$1,011.3241	$1,011.32	$1,011.30	$1,011.30