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	$115.59	9.331%	$126.3757	$126.38	$126.40	$126.40
Purchase #2	$227.67	4.624%	$238.1975	$238.20	$238.20	$238.20
Purchase #3	$181.79	3.332%	$187.8472	$187.85	$187.85	$187.80
Purchase #4	$89.46	6.486%	$95.2624	$95.26	$95.25	$95.30
Purchase #5	$190.71	4.811%	$199.8851	$199.89	$199.90	$199.90
Purchase #6	$46.85	8.341%	$50.7578	$50.76	$50.75	$50.80
Purchase #7	$64.60	10.855%	$71.6123	$71.61	$71.60	$71.60
7 purchase totals =	$916.67		$969.9380	$969.95	$969.95	$970.00