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	$51.35	11.162%	$57.0817	$57.08	$57.10	$57.10
Purchase #2	$232.86	5.869%	$246.5266	$246.53	$246.55	$246.50
Purchase #3	$105.95	11.740%	$118.3885	$118.39	$118.40	$118.40
Purchase #4	$136.90	8.524%	$148.5694	$148.57	$148.55	$148.60
Purchase #5	$150.72	9.863%	$165.5855	$165.59	$165.60	$165.60
Purchase #6	$187.39	5.798%	$198.2549	$198.25	$198.25	$198.30
Purchase #7	$144.28	12.445%	$162.2356	$162.24	$162.25	$162.20
7 purchase totals =	$1,009.45		$1,096.6422	$1,096.65	$1,096.70	$1,096.70