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	$35.51	9.188%	$38.7727	$38.77	$38.75	$38.80
Purchase #2	$98.80	11.663%	$110.323	$110.32	$110.30	$110.30
Purchase #3	$222.40	11.745%	$248.5209	$248.52	$248.50	$248.50
Purchase #4	$141.98	9.806%	$155.9026	$155.90	$155.90	$155.90
Purchase #5	$150.43	9.611%	$164.8878	$164.89	$164.90	$164.90
Purchase #6	$216.79	7.749%	$233.5891	$233.59	$233.60	$233.60
Purchase #7	$79.44	4.589%	$83.0855	$83.09	$83.10	$83.10
7 purchase totals =	$945.35		$1,035.0816	$1,035.08	$1,035.05	$1,035.10