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	$231.33	9.768%	$253.9263	$253.93	$253.95	$253.90
Purchase #2	$32.94	12.268%	$36.9811	$36.98	$37.00	$37.00
Purchase #3	$103.75	5.228%	$109.1741	$109.17	$109.15	$109.20
Purchase #4	$246.85	13.690%	$280.6438	$280.64	$280.65	$280.60
Purchase #5	$83.87	6.706%	$89.4943	$89.49	$89.50	$89.50
Purchase #6	$25.45	12.801%	$28.7079	$28.71	$28.70	$28.70
Purchase #7	$132.70	11.545%	$148.0202	$148.02	$148.00	$148.00
7 purchase totals =	$856.89		$946.9477	$946.94	$946.95	$946.90