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	$226.33	6.697%	$241.4873	$241.49	$241.50	$241.50
Purchase #2	$192.28	3.253%	$198.5349	$198.53	$198.55	$198.50
Purchase #3	$13.97	7.423%	$15.007	$15.01	$15.00	$15.00
Purchase #4	$209.41	3.372%	$216.4713	$216.47	$216.45	$216.50
Purchase #5	$130.57	3.217%	$134.7704	$134.77	$134.75	$134.80
Purchase #6	$114.35	11.582%	$127.594	$127.59	$127.60	$127.60
Purchase #7	$44.59	6.821%	$47.6315	$47.63	$47.65	$47.60
7 purchase totals =	$931.50		$981.4964	$981.49	$981.50	$981.50