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	$248.38	10.686%	$274.9219	$274.92	$274.90	$274.90
Purchase #2	$176.33	13.454%	$200.0534	$200.05	$200.05	$200.10
Purchase #3	$126.89	10.621%	$140.367	$140.37	$140.35	$140.40
Purchase #4	$118.43	11.432%	$131.9689	$131.97	$131.95	$132.00
Purchase #5	$190.99	4.797%	$200.1518	$200.15	$200.15	$200.20
Purchase #6	$110.84	8.164%	$119.889	$119.89	$119.90	$119.90
Purchase #7	$118.96	6.791%	$127.0386	$127.04	$127.05	$127.00
7 purchase totals =	$1,090.82		$1,194.3906	$1,194.39	$1,194.35	$1,194.50