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	$101.29	3.143%	$104.4735	$104.47	$104.45	$104.50
Purchase #2	$104.59	10.365%	$115.4308	$115.43	$115.45	$115.40
Purchase #3	$66.43	9.637%	$72.8319	$72.83	$72.85	$72.80
Purchase #4	$20.97	13.788%	$23.8613	$23.86	$23.85	$23.90
Purchase #5	$119.95	3.498%	$124.1459	$124.15	$124.15	$124.10
Purchase #6	$156.57	4.838%	$164.1449	$164.14	$164.15	$164.10
Purchase #7	$174.47	3.428%	$180.4508	$180.45	$180.45	$180.50
7 purchase totals =	$744.27		$785.3391	$785.33	$785.35	$785.30