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	$120.64	5.257%	$126.982	$126.98	$127.00	$127.00
Purchase #2	$244.69	8.140%	$264.6078	$264.61	$264.60	$264.60
Purchase #3	$249.72	9.313%	$272.9764	$272.98	$273.00	$273.00
Purchase #4	$72.89	5.484%	$76.8873	$76.89	$76.90	$76.90
Purchase #5	$185.38	13.171%	$209.7964	$209.80	$209.80	$209.80
Purchase #6	$94.58	4.192%	$98.5448	$98.54	$98.55	$98.50
Purchase #7	$161.99	7.426%	$174.0194	$174.02	$174.00	$174.00
7 purchase totals =	$1,129.89		$1,223.8141	$1,223.82	$1,223.85	$1,223.80