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	$98.48	8.291%	$106.645	$106.65	$106.65	$106.60
Purchase #2	$136.25	6.293%	$144.8242	$144.82	$144.80	$144.80
Purchase #3	$138.86	3.453%	$143.6548	$143.65	$143.65	$143.70
Purchase #4	$140.88	13.466%	$159.8509	$159.85	$159.85	$159.90
Purchase #5	$199.91	6.861%	$213.6258	$213.63	$213.65	$213.60
Purchase #6	$155.53	5.854%	$164.6347	$164.63	$164.65	$164.60
Purchase #7	$67.27	7.163%	$72.0886	$72.09	$72.10	$72.10
7 purchase totals =	$937.18		$1,005.3240	$1,005.32	$1,005.35	$1,005.30