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	$162.90	10.770%	$180.4443	$180.44	$180.45	$180.40
Purchase #2	$165.59	9.561%	$181.4221	$181.42	$181.40	$181.40
Purchase #3	$42.71	9.733%	$46.867	$46.87	$46.85	$46.90
Purchase #4	$82.85	10.551%	$91.5915	$91.59	$91.60	$91.60
Purchase #5	$207.69	11.833%	$232.266	$232.27	$232.25	$232.30
Purchase #6	$176.89	7.333%	$189.8613	$189.86	$189.85	$189.90
Purchase #7	$138.96	6.676%	$148.237	$148.24	$148.25	$148.20
7 purchase totals =	$977.59		$1,070.6892	$1,070.69	$1,070.65	$1,070.70