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	$177.28	10.818%	$196.4582	$196.46	$196.45	$196.50
Purchase #2	$85.41	3.173%	$88.1201	$88.12	$88.10	$88.10
Purchase #3	$131.44	13.827%	$149.6142	$149.61	$149.60	$149.60
Purchase #4	$233.35	12.478%	$262.4674	$262.47	$262.45	$262.50
Purchase #5	$190.42	9.291%	$208.1119	$208.11	$208.10	$208.10
Purchase #6	$185.87	5.732%	$196.5241	$196.52	$196.50	$196.50
Purchase #7	$143.34	3.325%	$148.1061	$148.11	$148.10	$148.10
7 purchase totals =	$1,147.11		$1,249.4020	$1,249.40	$1,249.30	$1,249.40