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	$136.79	3.579%	$141.6857	$141.69	$141.70	$141.70
Purchase #2	$171.41	4.161%	$178.5424	$178.54	$178.55	$178.50
Purchase #3	$188.53	11.827%	$210.8274	$210.83	$210.85	$210.80
Purchase #4	$42.27	10.492%	$46.705	$46.71	$46.70	$46.70
Purchase #5	$156.45	7.817%	$168.6797	$168.68	$168.70	$168.70
Purchase #6	$54.40	5.187%	$57.2217	$57.22	$57.20	$57.20
Purchase #7	$222.56	7.181%	$238.542	$238.54	$238.55	$238.50
7 purchase totals =	$972.41		$1,042.2039	$1,042.21	$1,042.25	$1,042.10