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	$164.47	13.202%	$186.1833	$186.18	$186.20	$186.20
Purchase #2	$155.47	5.834%	$164.5401	$164.54	$164.55	$164.50
Purchase #3	$89.57	5.869%	$94.8269	$94.83	$94.85	$94.80
Purchase #4	$179.25	11.853%	$200.4965	$200.50	$200.50	$200.50
Purchase #5	$50.29	9.417%	$55.0258	$55.03	$55.05	$55.00
Purchase #6	$182.63	8.471%	$198.1006	$198.10	$198.10	$198.10
Purchase #7	$169.72	6.563%	$180.8587	$180.86	$180.85	$180.90
7 purchase totals =	$991.40		$1,080.0319	$1,080.04	$1,080.10	$1,080.00