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	$86.32	3.742%	$89.5501	$89.55	$89.55	$89.60
Purchase #2	$31.72	3.164%	$32.7236	$32.72	$32.70	$32.70
Purchase #3	$223.42	7.219%	$239.5487	$239.55	$239.55	$239.50
Purchase #4	$147.39	6.221%	$156.5591	$156.56	$156.55	$156.60
Purchase #5	$126.26	5.257%	$132.8975	$132.90	$132.90	$132.90
Purchase #6	$98.82	11.124%	$109.8127	$109.81	$109.80	$109.80
Purchase #7	$96.47	7.295%	$103.5075	$103.51	$103.50	$103.50
7 purchase totals =	$810.40		$864.5992	$864.60	$864.55	$864.60