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	$91.76	6.359%	$97.595	$97.60	$97.60	$97.60
Purchase #2	$86.85	11.790%	$97.0896	$97.09	$97.10	$97.10
Purchase #3	$117.91	3.715%	$122.2904	$122.29	$122.30	$122.30
Purchase #4	$237.76	11.860%	$265.9583	$265.96	$265.95	$266.00
Purchase #5	$205.61	10.628%	$227.4622	$227.46	$227.45	$227.50
Purchase #6	$96.53	6.164%	$102.4801	$102.48	$102.50	$102.50
Purchase #7	$98.73	5.443%	$104.1039	$104.10	$104.10	$104.10
7 purchase totals =	$935.15		$1,016.9795	$1,016.98	$1,017.00	$1,017.10