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	$245.44	11.565%	$273.8251	$273.83	$273.85	$273.80
Purchase #2	$54.78	10.542%	$60.5549	$60.55	$60.55	$60.60
Purchase #3	$232.27	3.570%	$240.562	$240.56	$240.55	$240.60
Purchase #4	$12.29	9.831%	$13.4982	$13.50	$13.50	$13.50
Purchase #5	$104.40	11.356%	$116.2557	$116.26	$116.25	$116.30
Purchase #6	$44.46	4.807%	$46.5972	$46.60	$46.60	$46.60
Purchase #7	$247.46	3.315%	$255.6633	$255.66	$255.65	$255.70
7 purchase totals =	$941.10		$1,006.9564	$1,006.96	$1,006.95	$1,007.10