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	$214.27	13.293%	$242.7529	$242.75	$242.75	$242.80
Purchase #2	$240.85	10.330%	$265.7298	$265.73	$265.75	$265.70
Purchase #3	$158.50	6.177%	$168.2905	$168.29	$168.30	$168.30
Purchase #4	$162.60	4.247%	$169.5056	$169.51	$169.50	$169.50
Purchase #5	$227.93	9.586%	$249.7794	$249.78	$249.80	$249.80
Purchase #6	$166.98	7.753%	$179.926	$179.93	$179.95	$179.90
Purchase #7	$209.98	6.125%	$222.8413	$222.84	$222.85	$222.80
7 purchase totals =	$1,381.11		$1,498.8255	$1,498.83	$1,498.90	$1,498.80