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	$111.93	4.403%	$116.8583	$116.86	$116.85	$116.90
Purchase #2	$90.61	4.676%	$94.8469	$94.85	$94.85	$94.80
Purchase #3	$215.96	12.349%	$242.6289	$242.63	$242.65	$242.60
Purchase #4	$6.62	9.334%	$7.2379	$7.24	$7.25	$7.20
Purchase #5	$136.66	5.462%	$144.1244	$144.12	$144.10	$144.10
Purchase #6	$194.38	9.534%	$212.9122	$212.91	$212.90	$212.90
Purchase #7	$54.26	10.220%	$59.8054	$59.81	$59.80	$59.80
7 purchase totals =	$810.42		$878.4140	$878.42	$878.40	$878.30