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	$122.30	7.426%	$131.382	$131.38	$131.40	$131.40
Purchase #2	$182.82	9.677%	$200.5115	$200.51	$200.50	$200.50
Purchase #3	$185.84	8.235%	$201.1439	$201.14	$201.15	$201.10
Purchase #4	$67.73	7.700%	$72.9452	$72.95	$72.95	$72.90
Purchase #5	$86.71	13.197%	$98.1531	$98.15	$98.15	$98.20
Purchase #6	$83.46	12.837%	$94.1738	$94.17	$94.15	$94.20
Purchase #7	$107.69	3.300%	$111.2438	$111.24	$111.25	$111.20
7 purchase totals =	$836.55		$909.5533	$909.54	$909.55	$909.50