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	$126.27	12.317%	$141.8227	$141.82	$141.80	$141.80
Purchase #2	$30.89	9.705%	$33.8879	$33.89	$33.90	$33.90
Purchase #3	$244.59	9.224%	$267.151	$267.15	$267.15	$267.20
Purchase #4	$41.96	9.709%	$46.0339	$46.03	$46.05	$46.00
Purchase #5	$198.82	9.108%	$216.9285	$216.93	$216.95	$216.90
Purchase #6	$80.71	12.132%	$90.5017	$90.50	$90.50	$90.50
Purchase #7	$110.67	5.254%	$116.4846	$116.48	$116.50	$116.50
7 purchase totals =	$833.91		$912.8103	$912.80	$912.85	$912.80