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	$218.94	10.650%	$242.2571	$242.26	$242.25	$242.30
Purchase #2	$151.60	3.359%	$156.6922	$156.69	$156.70	$156.70
Purchase #3	$241.85	6.222%	$256.8979	$256.90	$256.90	$256.90
Purchase #4	$137.48	4.225%	$143.2885	$143.29	$143.30	$143.30
Purchase #5	$29.41	10.524%	$32.5051	$32.51	$32.50	$32.50
Purchase #6	$195.62	10.117%	$215.4109	$215.41	$215.40	$215.40
Purchase #7	$236.52	10.148%	$260.522	$260.52	$260.50	$260.50
7 purchase totals =	$1,211.42		$1,307.5737	$1,307.58	$1,307.55	$1,307.60