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	$118.98	10.851%	$131.8905	$131.89	$131.90	$131.90
Purchase #2	$218.32	4.493%	$228.1291	$228.13	$228.15	$228.10
Purchase #3	$95.81	4.869%	$100.475	$100.48	$100.50	$100.50
Purchase #4	$175.94	13.240%	$199.2345	$199.23	$199.25	$199.20
Purchase #5	$248.53	10.291%	$274.1062	$274.11	$274.10	$274.10
Purchase #6	$111.76	10.823%	$123.8558	$123.86	$123.85	$123.90
Purchase #7	$106.58	3.619%	$110.4371	$110.44	$110.45	$110.40
7 purchase totals =	$1,075.92		$1,168.1282	$1,168.14	$1,168.20	$1,168.10