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	$128.34	13.828%	$146.0869	$146.09	$146.10	$146.10
Purchase #2	$213.59	12.273%	$239.8039	$239.80	$239.80	$239.80
Purchase #3	$223.42	11.572%	$249.2742	$249.27	$249.25	$249.30
Purchase #4	$190.38	9.682%	$208.8126	$208.81	$208.80	$208.80
Purchase #5	$35.82	3.582%	$37.1031	$37.10	$37.10	$37.10
Purchase #6	$38.76	5.841%	$41.024	$41.02	$41.00	$41.00
Purchase #7	$161.51	13.393%	$183.141	$183.14	$183.15	$183.10
7 purchase totals =	$991.82		$1,105.2457	$1,105.23	$1,105.20	$1,105.20