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	$63.96	12.114%	$71.7081	$71.71	$71.70	$71.70
Purchase #2	$132.57	11.656%	$148.0224	$148.02	$148.00	$148.00
Purchase #3	$43.77	4.180%	$45.5996	$45.60	$45.60	$45.60
Purchase #4	$245.77	6.637%	$262.0818	$262.08	$262.10	$262.10
Purchase #5	$241.66	3.170%	$249.3206	$249.32	$249.30	$249.30
Purchase #6	$207.58	9.642%	$227.5949	$227.59	$227.60	$227.60
Purchase #7	$67.69	13.550%	$76.862	$76.86	$76.85	$76.90
7 purchase totals =	$1,003.00		$1,081.1894	$1,081.18	$1,081.15	$1,081.20