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	$200.89	10.801%	$222.5881	$222.59	$222.60	$222.60
Purchase #2	$190.51	7.765%	$205.3031	$205.30	$205.30	$205.30
Purchase #3	$88.69	3.642%	$91.9201	$91.92	$91.90	$91.90
Purchase #4	$219.83	9.436%	$240.5732	$240.57	$240.55	$240.60
Purchase #5	$246.34	10.803%	$272.9521	$272.95	$272.95	$273.00
Purchase #6	$129.77	7.640%	$139.6844	$139.68	$139.70	$139.70
Purchase #7	$10.86	6.144%	$11.5272	$11.53	$11.55	$11.50
7 purchase totals =	$1,086.89		$1,184.5482	$1,184.54	$1,184.55	$1,184.60