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	$182.91	7.593%	$196.7984	$196.80	$196.80	$196.80
Purchase #2	$221.62	6.362%	$235.7195	$235.72	$235.70	$235.70
Purchase #3	$86.78	3.479%	$89.7991	$89.80	$89.80	$89.80
Purchase #4	$91.45	10.135%	$100.7185	$100.72	$100.70	$100.70
Purchase #5	$112.44	3.874%	$116.7959	$116.80	$116.80	$116.80
Purchase #6	$78.25	11.477%	$87.2308	$87.23	$87.25	$87.20
Purchase #7	$202.62	6.361%	$215.5087	$215.51	$215.50	$215.50
7 purchase totals =	$976.07		$1,042.5709	$1,042.58	$1,042.55	$1,042.50