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	$109.83	13.423%	$124.5725	$124.57	$124.55	$124.60
Purchase #2	$211.83	3.200%	$218.6086	$218.61	$218.60	$218.60
Purchase #3	$166.38	7.300%	$178.5257	$178.53	$178.55	$178.50
Purchase #4	$45.64	3.727%	$47.341	$47.34	$47.35	$47.30
Purchase #5	$150.64	13.650%	$171.2024	$171.20	$171.20	$171.20
Purchase #6	$152.57	9.459%	$167.0016	$167.00	$167.00	$167.00
Purchase #7	$95.85	13.563%	$108.8501	$108.85	$108.85	$108.90
7 purchase totals =	$932.74		$1,016.1019	$1,016.10	$1,016.10	$1,016.10