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	$192.73	9.414%	$210.8736	$210.87	$210.85	$210.90
Purchase #2	$84.89	5.206%	$89.3094	$89.31	$89.30	$89.30
Purchase #3	$101.35	11.356%	$112.8593	$112.86	$112.85	$112.90
Purchase #4	$232.76	9.807%	$255.5868	$255.59	$255.60	$255.60
Purchase #5	$104.39	8.323%	$113.0784	$113.08	$113.10	$113.10
Purchase #6	$51.57	13.133%	$58.3427	$58.34	$58.35	$58.30
Purchase #7	$96.34	7.491%	$103.5568	$103.56	$103.55	$103.60
7 purchase totals =	$864.03		$943.6070	$943.61	$943.60	$943.70