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	$95.84	5.331%	$100.9492	$100.95	$100.95	$100.90
Purchase #2	$99.69	13.765%	$113.4123	$113.41	$113.40	$113.40
Purchase #3	$93.58	5.712%	$98.9253	$98.93	$98.95	$98.90
Purchase #4	$185.82	3.702%	$192.6991	$192.70	$192.70	$192.70
Purchase #5	$100.72	11.137%	$111.9372	$111.94	$111.95	$111.90
Purchase #6	$108.56	4.483%	$113.4267	$113.43	$113.45	$113.40
Purchase #7	$83.81	4.273%	$87.3912	$87.39	$87.40	$87.40
7 purchase totals =	$768.02		$818.7410	$818.75	$818.80	$818.60