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	$30.54	7.255%	$32.7557	$32.76	$32.75	$32.80
Purchase #2	$82.69	12.281%	$92.8452	$92.85	$92.85	$92.80
Purchase #3	$163.94	13.185%	$185.5555	$185.56	$185.55	$185.60
Purchase #4	$208.39	3.145%	$214.9439	$214.94	$214.95	$214.90
Purchase #5	$6.51	5.804%	$6.8878	$6.89	$6.90	$6.90
Purchase #6	$131.59	10.535%	$145.453	$145.45	$145.45	$145.50
Purchase #7	$169.64	9.695%	$186.0866	$186.09	$186.10	$186.10
7 purchase totals =	$793.30		$864.5277	$864.54	$864.55	$864.60