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	$223.63	7.692%	$240.8316	$240.83	$240.85	$240.80
Purchase #2	$78.94	4.418%	$82.4276	$82.43	$82.45	$82.40
Purchase #3	$209.29	9.212%	$228.5698	$228.57	$228.55	$228.60
Purchase #4	$61.95	13.259%	$70.164	$70.16	$70.15	$70.20
Purchase #5	$8.38	5.670%	$8.8551	$8.86	$8.85	$8.90
Purchase #6	$123.50	13.745%	$140.4751	$140.48	$140.50	$140.50
Purchase #7	$200.94	12.151%	$225.3562	$225.36	$225.35	$225.40
7 purchase totals =	$906.63		$996.6794	$996.69	$996.70	$996.80