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	$136.33	4.481%	$142.4389	$142.44	$142.45	$142.40
Purchase #2	$196.70	9.755%	$215.8881	$215.89	$215.90	$215.90
Purchase #3	$87.74	13.365%	$99.4665	$99.47	$99.45	$99.50
Purchase #4	$199.59	4.507%	$208.5855	$208.59	$208.60	$208.60
Purchase #5	$242.91	4.717%	$254.3681	$254.37	$254.35	$254.40
Purchase #6	$99.63	7.392%	$106.9946	$106.99	$107.00	$107.00
Purchase #7	$64.59	6.194%	$68.5907	$68.59	$68.60	$68.60
7 purchase totals =	$1,027.49		$1,096.3324	$1,096.34	$1,096.35	$1,096.40