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	$31.66	3.681%	$32.8254	$32.83	$32.85	$32.80
Purchase #2	$18.96	11.563%	$21.1523	$21.15	$21.15	$21.20
Purchase #3	$214.44	13.713%	$243.8462	$243.85	$243.85	$243.80
Purchase #4	$157.63	5.299%	$165.9828	$165.98	$166.00	$166.00
Purchase #5	$192.44	5.488%	$203.0011	$203.00	$203.00	$203.00
Purchase #6	$173.85	9.644%	$190.6161	$190.62	$190.60	$190.60
Purchase #7	$178.27	10.441%	$196.8832	$196.88	$196.90	$196.90
7 purchase totals =	$967.25		$1,054.3071	$1,054.31	$1,054.35	$1,054.30