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	$41.41	9.587%	$45.38	$45.38	$45.40	$45.40
Purchase #2	$169.73	9.316%	$185.542	$185.54	$185.55	$185.50
Purchase #3	$225.61	3.681%	$233.9147	$233.91	$233.90	$233.90
Purchase #4	$219.44	13.256%	$248.529	$248.53	$248.55	$248.50
Purchase #5	$74.39	8.337%	$80.5919	$80.59	$80.60	$80.60
Purchase #6	$185.48	6.522%	$197.577	$197.58	$197.60	$197.60
Purchase #7	$204.80	9.630%	$224.5222	$224.52	$224.50	$224.50
7 purchase totals =	$1,120.86		$1,216.0568	$1,216.05	$1,216.10	$1,216.00