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	$213.88	5.219%	$225.0424	$225.04	$225.05	$225.00
Purchase #2	$108.79	10.733%	$120.4664	$120.47	$120.45	$120.50
Purchase #3	$82.46	8.539%	$89.5013	$89.50	$89.50	$89.50
Purchase #4	$240.36	8.524%	$260.8483	$260.85	$260.85	$260.80
Purchase #5	$107.36	4.574%	$112.2706	$112.27	$112.25	$112.30
Purchase #6	$67.32	7.524%	$72.3852	$72.39	$72.40	$72.40
Purchase #7	$210.25	8.139%	$227.3622	$227.36	$227.35	$227.40
7 purchase totals =	$1,030.42		$1,107.8764	$1,107.88	$1,107.85	$1,107.90