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	$78.55	13.843%	$89.4237	$89.42	$89.40	$89.40
Purchase #2	$119.26	13.253%	$135.0655	$135.07	$135.05	$135.10
Purchase #3	$142.32	4.202%	$148.3003	$148.30	$148.30	$148.30
Purchase #4	$170.40	7.404%	$183.0164	$183.02	$183.00	$183.00
Purchase #5	$83.52	7.565%	$89.8383	$89.84	$89.85	$89.80
Purchase #6	$217.71	7.641%	$234.3452	$234.35	$234.35	$234.30
Purchase #7	$222.51	5.427%	$234.5856	$234.59	$234.60	$234.60
7 purchase totals =	$1,034.27		$1,114.5750	$1,114.59	$1,114.55	$1,114.50