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	$200.72	8.256%	$217.2914	$217.29	$217.30	$217.30
Purchase #2	$101.56	8.367%	$110.0575	$110.06	$110.05	$110.10
Purchase #3	$153.63	11.695%	$171.597	$171.60	$171.60	$171.60
Purchase #4	$128.61	6.172%	$136.5478	$136.55	$136.55	$136.50
Purchase #5	$51.27	11.789%	$57.3142	$57.31	$57.30	$57.30
Purchase #6	$219.81	9.266%	$240.1776	$240.18	$240.20	$240.20
Purchase #7	$81.81	11.113%	$90.9015	$90.90	$90.90	$90.90
7 purchase totals =	$937.41		$1,023.8870	$1,023.89	$1,023.90	$1,023.90