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	$239.47	11.870%	$267.8951	$267.90	$267.90	$267.90
Purchase #2	$72.29	11.422%	$80.547	$80.55	$80.55	$80.50
Purchase #3	$90.84	10.573%	$100.4445	$100.44	$100.45	$100.40
Purchase #4	$196.80	6.413%	$209.4208	$209.42	$209.40	$209.40
Purchase #5	$44.78	9.502%	$49.035	$49.04	$49.05	$49.00
Purchase #6	$109.73	4.733%	$114.9235	$114.92	$114.90	$114.90
Purchase #7	$238.89	6.426%	$254.2411	$254.24	$254.25	$254.20
7 purchase totals =	$992.80		$1,076.5070	$1,076.51	$1,076.50	$1,076.30