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	$30.91	5.206%	$32.5192	$32.52	$32.50	$32.50
Purchase #2	$164.94	3.735%	$171.1005	$171.10	$171.10	$171.10
Purchase #3	$134.51	10.165%	$148.1829	$148.18	$148.20	$148.20
Purchase #4	$172.40	12.576%	$194.081	$194.08	$194.10	$194.10
Purchase #5	$161.98	6.866%	$173.1015	$173.10	$173.10	$173.10
Purchase #6	$228.33	6.794%	$243.8427	$243.84	$243.85	$243.80
Purchase #7	$91.94	7.508%	$98.8429	$98.84	$98.85	$98.80
7 purchase totals =	$985.01		$1,061.6707	$1,061.66	$1,061.70	$1,061.60