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	$72.60	8.186%	$78.543	$78.54	$78.55	$78.50
Purchase #2	$116.31	7.242%	$124.7332	$124.73	$124.75	$124.70
Purchase #3	$142.40	7.273%	$152.7568	$152.76	$152.75	$152.80
Purchase #4	$241.85	4.143%	$251.8698	$251.87	$251.85	$251.90
Purchase #5	$180.96	9.107%	$197.44	$197.44	$197.45	$197.40
Purchase #6	$63.33	12.853%	$71.4698	$71.47	$71.45	$71.50
Purchase #7	$134.72	3.534%	$139.481	$139.48	$139.50	$139.50
7 purchase totals =	$952.17		$1,016.2936	$1,016.29	$1,016.30	$1,016.30