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	$130.91	13.695%	$148.8381	$148.84	$148.85	$148.80
Purchase #2	$169.53	7.353%	$181.9955	$182.00	$182.00	$182.00
Purchase #3	$164.36	4.319%	$171.4587	$171.46	$171.45	$171.50
Purchase #4	$40.43	13.310%	$45.8112	$45.81	$45.80	$45.80
Purchase #5	$101.51	7.566%	$109.1902	$109.19	$109.20	$109.20
Purchase #6	$224.51	6.855%	$239.9002	$239.90	$239.90	$239.90
Purchase #7	$208.88	6.592%	$222.6494	$222.65	$222.65	$222.60
7 purchase totals =	$1,040.13		$1,119.8433	$1,119.85	$1,119.85	$1,119.80