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	$131.59	4.672%	$137.7379	$137.74	$137.75	$137.70
Purchase #2	$162.81	6.204%	$172.9107	$172.91	$172.90	$172.90
Purchase #3	$36.99	8.365%	$40.0842	$40.08	$40.10	$40.10
Purchase #4	$159.46	8.417%	$172.8817	$172.88	$172.90	$172.90
Purchase #5	$229.75	3.491%	$237.7706	$237.77	$237.75	$237.80
Purchase #6	$143.78	12.546%	$161.8186	$161.82	$161.80	$161.80
Purchase #7	$171.94	6.163%	$182.5367	$182.54	$182.55	$182.50
7 purchase totals =	$1,036.32		$1,105.7404	$1,105.74	$1,105.75	$1,105.70