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	$212.86	9.869%	$233.8672	$233.87	$233.85	$233.90
Purchase #2	$91.90	10.794%	$101.8197	$101.82	$101.80	$101.80
Purchase #3	$163.39	10.796%	$181.0296	$181.03	$181.05	$181.00
Purchase #4	$201.80	4.255%	$210.3866	$210.39	$210.40	$210.40
Purchase #5	$88.26	13.862%	$100.4946	$100.49	$100.50	$100.50
Purchase #6	$24.47	4.319%	$25.5269	$25.53	$25.55	$25.50
Purchase #7	$215.82	7.353%	$231.6892	$231.69	$231.70	$231.70
7 purchase totals =	$998.50		$1,084.8138	$1,084.82	$1,084.85	$1,084.80