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	$49.60	8.711%	$53.9207	$53.92	$53.90	$53.90
Purchase #2	$38.83	3.372%	$40.1393	$40.14	$40.15	$40.10
Purchase #3	$238.40	7.417%	$256.0821	$256.08	$256.10	$256.10
Purchase #4	$239.67	8.694%	$260.5069	$260.51	$260.50	$260.50
Purchase #5	$113.43	4.496%	$118.5298	$118.53	$118.55	$118.50
Purchase #6	$200.46	7.808%	$216.1119	$216.11	$216.10	$216.10
Purchase #7	$81.33	9.156%	$88.7766	$88.78	$88.80	$88.80
7 purchase totals =	$961.72		$1,034.0673	$1,034.07	$1,034.10	$1,034.00