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	$198.98	5.304%	$209.5339	$209.53	$209.55	$209.50
Purchase #2	$69.64	13.177%	$78.8165	$78.82	$78.80	$78.80
Purchase #3	$58.76	9.134%	$64.1271	$64.13	$64.15	$64.10
Purchase #4	$38.62	12.641%	$43.502	$43.50	$43.50	$43.50
Purchase #5	$144.80	9.226%	$158.1592	$158.16	$158.15	$158.20
Purchase #6	$230.85	8.709%	$250.9547	$250.95	$250.95	$251.00
Purchase #7	$196.76	10.660%	$217.7346	$217.73	$217.75	$217.70
7 purchase totals =	$938.41		$1,022.8280	$1,022.82	$1,022.85	$1,022.80