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	$147.94	4.667%	$154.8444	$154.84	$154.85	$154.80
Purchase #2	$68.90	13.585%	$78.2601	$78.26	$78.25	$78.30
Purchase #3	$67.71	12.149%	$75.9361	$75.94	$75.95	$75.90
Purchase #4	$81.69	13.347%	$92.5932	$92.59	$92.60	$92.60
Purchase #5	$61.64	4.256%	$64.2634	$64.26	$64.25	$64.30
Purchase #6	$133.29	13.428%	$151.1882	$151.19	$151.20	$151.20
Purchase #7	$40.50	8.127%	$43.7914	$43.79	$43.80	$43.80
7 purchase totals =	$601.67		$660.8768	$660.87	$660.90	$660.90