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	$59.32	5.454%	$62.5553	$62.56	$62.55	$62.60
Purchase #2	$139.50	6.665%	$148.7977	$148.80	$148.80	$148.80
Purchase #3	$220.42	12.122%	$247.1393	$247.14	$247.15	$247.10
Purchase #4	$158.71	4.523%	$165.8885	$165.89	$165.90	$165.90
Purchase #5	$108.57	7.663%	$116.8897	$116.89	$116.90	$116.90
Purchase #6	$68.84	5.825%	$72.8499	$72.85	$72.85	$72.80
Purchase #7	$109.84	12.806%	$123.9061	$123.91	$123.90	$123.90
7 purchase totals =	$865.20		$938.0265	$938.04	$938.05	$938.00