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	$246.73	5.159%	$259.4588	$259.46	$259.45	$259.50
Purchase #2	$201.38	12.497%	$226.5465	$226.55	$226.55	$226.50
Purchase #3	$91.79	13.410%	$104.099	$104.10	$104.10	$104.10
Purchase #4	$11.38	3.305%	$11.7561	$11.76	$11.75	$11.80
Purchase #5	$241.29	3.364%	$249.407	$249.41	$249.40	$249.40
Purchase #6	$242.45	5.334%	$255.3823	$255.38	$255.40	$255.40
Purchase #7	$161.39	7.503%	$173.4991	$173.50	$173.50	$173.50
7 purchase totals =	$1,196.41		$1,280.1488	$1,280.16	$1,280.15	$1,280.20