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	$246.79	4.807%	$258.6532	$258.65	$258.65	$258.70
Purchase #2	$127.35	3.780%	$132.1638	$132.16	$132.15	$132.20
Purchase #3	$85.55	8.469%	$92.7952	$92.80	$92.80	$92.80
Purchase #4	$217.47	6.121%	$230.7813	$230.78	$230.80	$230.80
Purchase #5	$33.67	11.506%	$37.5441	$37.54	$37.55	$37.50
Purchase #6	$163.79	3.132%	$168.9199	$168.92	$168.90	$168.90
Purchase #7	$118.92	10.719%	$131.667	$131.67	$131.65	$131.70
7 purchase totals =	$993.54		$1,052.5245	$1,052.52	$1,052.50	$1,052.60