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	$247.62	7.360%	$265.8448	$265.84	$265.85	$265.80
Purchase #2	$82.90	11.687%	$92.5885	$92.59	$92.60	$92.60
Purchase #3	$148.75	7.242%	$159.5225	$159.52	$159.50	$159.50
Purchase #4	$63.27	8.220%	$68.4708	$68.47	$68.45	$68.50
Purchase #5	$117.70	12.488%	$132.3984	$132.40	$132.40	$132.40
Purchase #6	$180.56	3.189%	$186.3181	$186.32	$186.30	$186.30
Purchase #7	$85.94	12.631%	$96.7951	$96.80	$96.80	$96.80
7 purchase totals =	$926.74		$1,001.9382	$1,001.94	$1,001.90	$1,001.90