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	$246.67	3.554%	$255.4367	$255.44	$255.45	$255.40
Purchase #2	$136.57	10.493%	$150.9003	$150.90	$150.90	$150.90
Purchase #3	$78.49	10.598%	$86.8084	$86.81	$86.80	$86.80
Purchase #4	$222.56	9.406%	$243.494	$243.49	$243.50	$243.50
Purchase #5	$220.79	7.642%	$237.6628	$237.66	$237.65	$237.70
Purchase #6	$181.54	9.446%	$198.6883	$198.69	$198.70	$198.70
Purchase #7	$103.65	7.339%	$111.2569	$111.26	$111.25	$111.30
7 purchase totals =	$1,190.27		$1,284.2474	$1,284.25	$1,284.25	$1,284.30