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	$93.46	5.463%	$98.5657	$98.57	$98.55	$98.60
Purchase #2	$43.98	6.257%	$46.7318	$46.73	$46.75	$46.70
Purchase #3	$250.43	12.136%	$280.8222	$280.82	$280.80	$280.80
Purchase #4	$59.50	7.378%	$63.8899	$63.89	$63.90	$63.90
Purchase #5	$31.33	4.426%	$32.7167	$32.72	$32.70	$32.70
Purchase #6	$119.72	5.586%	$126.4076	$126.41	$126.40	$126.40
Purchase #7	$243.93	5.285%	$256.8217	$256.82	$256.80	$256.80
7 purchase totals =	$842.35		$905.9556	$905.96	$905.90	$905.90