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	$191.60	4.712%	$200.6282	$200.63	$200.65	$200.60
Purchase #2	$217.34	9.185%	$237.3027	$237.30	$237.30	$237.30
Purchase #3	$26.80	6.230%	$28.4696	$28.47	$28.45	$28.50
Purchase #4	$175.25	8.627%	$190.3688	$190.37	$190.35	$190.40
Purchase #5	$176.45	3.632%	$182.8587	$182.86	$182.85	$182.90
Purchase #6	$125.69	9.637%	$137.8027	$137.80	$137.80	$137.80
Purchase #7	$104.82	4.746%	$109.7948	$109.79	$109.80	$109.80
7 purchase totals =	$1,017.95		$1,087.2255	$1,087.22	$1,087.20	$1,087.30