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	$152.83	4.254%	$159.3314	$159.33	$159.35	$159.30
Purchase #2	$135.35	11.180%	$150.4821	$150.48	$150.50	$150.50
Purchase #3	$156.75	8.305%	$169.7681	$169.77	$169.75	$169.80
Purchase #4	$39.31	9.651%	$43.1038	$43.10	$43.10	$43.10
Purchase #5	$103.47	7.618%	$111.3523	$111.35	$111.35	$111.40
Purchase #6	$101.99	3.254%	$105.3088	$105.31	$105.30	$105.30
Purchase #7	$203.70	11.737%	$227.6083	$227.61	$227.60	$227.60
7 purchase totals =	$893.40		$966.9548	$966.95	$966.95	$967.00