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	$34.65	6.806%	$37.0083	$37.01	$37.00	$37.00
Purchase #2	$88.79	5.430%	$93.6113	$93.61	$93.60	$93.60
Purchase #3	$101.54	8.296%	$109.9638	$109.96	$109.95	$110.00
Purchase #4	$6.71	11.509%	$7.4823	$7.48	$7.50	$7.50
Purchase #5	$127.40	5.227%	$134.0592	$134.06	$134.05	$134.10
Purchase #6	$42.93	7.582%	$46.185	$46.19	$46.20	$46.20
Purchase #7	$117.53	5.159%	$123.5934	$123.59	$123.60	$123.60
7 purchase totals =	$519.55		$551.9033	$551.90	$551.90	$552.00