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	$210.39	3.408%	$217.5601	$217.56	$217.55	$217.60
Purchase #2	$105.47	6.541%	$112.3688	$112.37	$112.35	$112.40
Purchase #3	$180.53	9.731%	$198.0974	$198.10	$198.10	$198.10
Purchase #4	$242.45	5.441%	$255.6417	$255.64	$255.65	$255.60
Purchase #5	$143.29	3.291%	$148.0057	$148.01	$148.00	$148.00
Purchase #6	$243.57	12.269%	$273.4536	$273.45	$273.45	$273.50
Purchase #7	$168.90	6.425%	$179.7518	$179.75	$179.75	$179.80
7 purchase totals =	$1,294.60		$1,384.8791	$1,384.88	$1,384.85	$1,385.00