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	$185.38	7.821%	$199.8786	$199.88	$199.90	$199.90
Purchase #2	$37.54	3.249%	$38.7597	$38.76	$38.75	$38.80
Purchase #3	$223.87	5.794%	$236.841	$236.84	$236.85	$236.80
Purchase #4	$126.72	3.188%	$130.7598	$130.76	$130.75	$130.80
Purchase #5	$154.70	6.822%	$165.2536	$165.25	$165.25	$165.30
Purchase #6	$131.38	3.659%	$136.1872	$136.19	$136.20	$136.20
Purchase #7	$176.45	11.542%	$196.8159	$196.82	$196.80	$196.80
7 purchase totals =	$1,036.04		$1,104.4958	$1,104.50	$1,104.50	$1,104.60