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	$72.73	7.874%	$78.4568	$78.46	$78.45	$78.50
Purchase #2	$227.50	8.682%	$247.2516	$247.25	$247.25	$247.30
Purchase #3	$36.60	13.324%	$41.4766	$41.48	$41.50	$41.50
Purchase #4	$90.86	3.694%	$94.2164	$94.22	$94.20	$94.20
Purchase #5	$109.61	4.747%	$114.8132	$114.81	$114.80	$114.80
Purchase #6	$166.46	12.592%	$187.4206	$187.42	$187.40	$187.40
Purchase #7	$238.40	6.218%	$253.2237	$253.22	$253.20	$253.20
7 purchase totals =	$942.16		$1,016.8589	$1,016.86	$1,016.80	$1,016.90