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	$32.69	10.823%	$36.228	$36.23	$36.25	$36.20
Purchase #2	$86.43	3.262%	$89.2493	$89.25	$89.25	$89.20
Purchase #3	$40.41	7.232%	$43.3325	$43.33	$43.35	$43.30
Purchase #4	$52.38	11.270%	$58.2832	$58.28	$58.30	$58.30
Purchase #5	$75.36	10.810%	$83.5064	$83.51	$83.50	$83.50
Purchase #6	$33.44	6.712%	$35.6845	$35.68	$35.70	$35.70
Purchase #7	$84.66	7.131%	$90.6971	$90.70	$90.70	$90.70
7 purchase totals =	$405.37		$436.9810	$436.98	$437.05	$436.90