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	$118.72	8.543%	$128.8622	$128.86	$128.85	$128.90
Purchase #2	$169.86	7.610%	$182.7863	$182.79	$182.80	$182.80
Purchase #3	$50.42	6.226%	$53.5591	$53.56	$53.55	$53.60
Purchase #4	$57.26	10.563%	$63.3084	$63.31	$63.30	$63.30
Purchase #5	$227.53	9.282%	$248.6493	$248.65	$248.65	$248.60
Purchase #6	$179.33	3.487%	$185.5832	$185.58	$185.60	$185.60
Purchase #7	$184.32	3.573%	$190.9058	$190.91	$190.90	$190.90
7 purchase totals =	$987.44		$1,053.6543	$1,053.66	$1,053.65	$1,053.70