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	$100.33	11.382%	$111.7496	$111.75	$111.75	$111.70
Purchase #2	$32.67	11.578%	$36.4525	$36.45	$36.45	$36.50
Purchase #3	$127.31	9.831%	$139.8258	$139.83	$139.85	$139.80
Purchase #4	$223.69	5.170%	$235.2548	$235.25	$235.25	$235.30
Purchase #5	$165.49	7.217%	$177.4334	$177.43	$177.45	$177.40
Purchase #6	$135.36	6.291%	$143.8755	$143.88	$143.90	$143.90
Purchase #7	$155.66	5.771%	$164.6431	$164.64	$164.65	$164.60
7 purchase totals =	$940.51		$1,009.2347	$1,009.23	$1,009.30	$1,009.20