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	$101.44	3.659%	$105.1517	$105.15	$105.15	$105.20
Purchase #2	$238.64	12.819%	$269.2313	$269.23	$269.25	$269.20
Purchase #3	$55.47	13.188%	$62.7854	$62.79	$62.80	$62.80
Purchase #4	$143.28	13.748%	$162.9781	$162.98	$163.00	$163.00
Purchase #5	$119.60	5.248%	$125.8766	$125.88	$125.90	$125.90
Purchase #6	$228.93	13.270%	$259.309	$259.31	$259.30	$259.30
Purchase #7	$76.53	7.325%	$82.1358	$82.14	$82.15	$82.10
7 purchase totals =	$963.89		$1,067.4679	$1,067.48	$1,067.55	$1,067.50