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	$192.40	3.288%	$198.7261	$198.73	$198.75	$198.70
Purchase #2	$87.40	5.725%	$92.4037	$92.40	$92.40	$92.40
Purchase #3	$49.73	8.463%	$53.9386	$53.94	$53.95	$53.90
Purchase #4	$97.57	3.117%	$100.6113	$100.61	$100.60	$100.60
Purchase #5	$81.50	12.165%	$91.4145	$91.41	$91.40	$91.40
Purchase #6	$245.79	9.792%	$269.8578	$269.86	$269.85	$269.90
Purchase #7	$187.87	13.627%	$213.471	$213.47	$213.45	$213.50
7 purchase totals =	$942.26		$1,020.4230	$1,020.42	$1,020.40	$1,020.40