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	$92.82	10.735%	$102.7842	$102.78	$102.80	$102.80
Purchase #2	$6.40	11.250%	$7.12	$7.12	$7.10	$7.10
Purchase #3	$196.81	7.154%	$210.8898	$210.89	$210.90	$210.90
Purchase #4	$158.59	11.282%	$176.4821	$176.48	$176.50	$176.50
Purchase #5	$81.50	13.354%	$92.3835	$92.38	$92.40	$92.40
Purchase #6	$108.72	4.534%	$113.6494	$113.65	$113.65	$113.60
Purchase #7	$115.54	10.571%	$127.7537	$127.75	$127.75	$127.80
7 purchase totals =	$760.38		$831.0627	$831.05	$831.10	$831.10