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	$89.93	5.443%	$94.8249	$94.82	$94.80	$94.80
Purchase #2	$136.96	11.602%	$152.8501	$152.85	$152.85	$152.90
Purchase #3	$138.71	8.666%	$150.7306	$150.73	$150.75	$150.70
Purchase #4	$228.94	8.646%	$248.7342	$248.73	$248.75	$248.70
Purchase #5	$61.56	9.758%	$67.567	$67.57	$67.55	$67.60
Purchase #6	$169.55	12.204%	$190.2419	$190.24	$190.25	$190.20
Purchase #7	$170.92	6.781%	$182.5101	$182.51	$182.50	$182.50
7 purchase totals =	$996.57		$1,087.4588	$1,087.45	$1,087.45	$1,087.40