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	$196.67	9.624%	$215.5975	$215.60	$215.60	$215.60
Purchase #2	$33.69	12.175%	$37.7918	$37.79	$37.80	$37.80
Purchase #3	$120.81	10.578%	$133.5893	$133.59	$133.60	$133.60
Purchase #4	$245.81	11.420%	$273.8815	$273.88	$273.90	$273.90
Purchase #5	$167.86	10.525%	$185.5273	$185.53	$185.55	$185.50
Purchase #6	$96.69	3.650%	$100.2192	$100.22	$100.20	$100.20
Purchase #7	$167.48	8.730%	$182.101	$182.10	$182.10	$182.10
7 purchase totals =	$1,029.01		$1,128.7076	$1,128.71	$1,128.75	$1,128.70