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	$132.50	6.226%	$140.7495	$140.75	$140.75	$140.70
Purchase #2	$159.57	13.750%	$181.5109	$181.51	$181.50	$181.50
Purchase #3	$208.66	12.656%	$235.068	$235.07	$235.05	$235.10
Purchase #4	$222.35	7.483%	$238.9885	$238.99	$239.00	$239.00
Purchase #5	$131.56	9.270%	$143.7556	$143.76	$143.75	$143.80
Purchase #6	$68.50	4.311%	$71.453	$71.45	$71.45	$71.50
Purchase #7	$189.72	3.714%	$196.7662	$196.77	$196.75	$196.80
7 purchase totals =	$1,112.86		$1,208.2917	$1,208.30	$1,208.25	$1,208.40