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	$239.47	13.798%	$272.5121	$272.51	$272.50	$272.50
Purchase #2	$33.63	4.415%	$35.1148	$35.11	$35.10	$35.10
Purchase #3	$207.60	12.375%	$233.2905	$233.29	$233.30	$233.30
Purchase #4	$69.82	12.842%	$78.7863	$78.79	$78.80	$78.80
Purchase #5	$203.79	8.673%	$221.4647	$221.46	$221.45	$221.50
Purchase #6	$119.70	3.449%	$123.8285	$123.83	$123.85	$123.80
Purchase #7	$86.90	8.276%	$94.0918	$94.09	$94.10	$94.10
7 purchase totals =	$960.91		$1,059.0887	$1,059.08	$1,059.10	$1,059.10