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	$197.91	3.546%	$204.9279	$204.93	$204.95	$204.90
Purchase #2	$185.66	5.667%	$196.1814	$196.18	$196.20	$196.20
Purchase #3	$230.76	4.375%	$240.8558	$240.86	$240.85	$240.90
Purchase #4	$38.54	12.195%	$43.24	$43.24	$43.25	$43.20
Purchase #5	$88.31	4.708%	$92.4676	$92.47	$92.45	$92.50
Purchase #6	$86.71	9.756%	$95.1694	$95.17	$95.15	$95.20
Purchase #7	$32.80	7.618%	$35.2987	$35.30	$35.30	$35.30
7 purchase totals =	$860.69		$908.1408	$908.15	$908.15	$908.20