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	$191.87	9.351%	$209.8118	$209.81	$209.80	$209.80
Purchase #2	$107.29	11.676%	$119.8172	$119.82	$119.80	$119.80
Purchase #3	$191.61	9.196%	$209.2305	$209.23	$209.25	$209.20
Purchase #4	$217.45	4.555%	$227.3548	$227.35	$227.35	$227.40
Purchase #5	$77.54	3.458%	$80.2213	$80.22	$80.20	$80.20
Purchase #6	$240.80	7.729%	$259.4114	$259.41	$259.40	$259.40
Purchase #7	$90.48	4.437%	$94.4946	$94.49	$94.50	$94.50
7 purchase totals =	$1,117.04		$1,200.3416	$1,200.33	$1,200.30	$1,200.30