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	$114.86	11.143%	$127.6588	$127.66	$127.65	$127.70
Purchase #2	$103.78	7.756%	$111.8292	$111.83	$111.85	$111.80
Purchase #3	$111.78	8.372%	$121.1382	$121.14	$121.15	$121.10
Purchase #4	$30.69	4.746%	$32.1465	$32.15	$32.15	$32.10
Purchase #5	$159.93	10.478%	$176.6875	$176.69	$176.70	$176.70
Purchase #6	$115.40	7.761%	$124.3562	$124.36	$124.35	$124.40
Purchase #7	$240.50	10.190%	$265.007	$265.01	$265.00	$265.00
7 purchase totals =	$876.94		$958.8234	$958.84	$958.85	$958.80