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	$53.46	6.468%	$56.9178	$56.92	$56.90	$56.90
Purchase #2	$227.25	12.592%	$255.8653	$255.87	$255.85	$255.90
Purchase #3	$65.84	10.785%	$72.9408	$72.94	$72.95	$72.90
Purchase #4	$248.34	12.763%	$280.0356	$280.04	$280.05	$280.00
Purchase #5	$77.62	10.731%	$85.9494	$85.95	$85.95	$85.90
Purchase #6	$204.89	13.539%	$232.6301	$232.63	$232.65	$232.60
Purchase #7	$69.54	7.510%	$74.7625	$74.76	$74.75	$74.80
7 purchase totals =	$946.94		$1,059.1015	$1,059.11	$1,059.10	$1,059.00