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	$159.28	3.502%	$164.858	$164.86	$164.85	$164.90
Purchase #2	$239.71	4.517%	$250.5377	$250.54	$250.55	$250.50
Purchase #3	$158.93	12.549%	$178.8741	$178.87	$178.85	$178.90
Purchase #4	$184.79	8.379%	$200.2736	$200.27	$200.25	$200.30
Purchase #5	$196.68	7.470%	$211.372	$211.37	$211.35	$211.40
Purchase #6	$61.35	8.627%	$66.6427	$66.64	$66.65	$66.60
Purchase #7	$130.55	6.702%	$139.2995	$139.30	$139.30	$139.30
7 purchase totals =	$1,131.29		$1,211.8576	$1,211.85	$1,211.80	$1,211.90