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	$76.80	7.705%	$82.7174	$82.72	$82.70	$82.70
Purchase #2	$215.77	4.481%	$225.4387	$225.44	$225.45	$225.40
Purchase #3	$89.63	3.381%	$92.6604	$92.66	$92.65	$92.70
Purchase #4	$223.34	9.859%	$245.3591	$245.36	$245.35	$245.40
Purchase #5	$129.87	8.288%	$140.6336	$140.63	$140.65	$140.60
Purchase #6	$141.61	7.670%	$152.4715	$152.47	$152.45	$152.50
Purchase #7	$154.35	6.607%	$164.5479	$164.55	$164.55	$164.50
7 purchase totals =	$1,031.37		$1,103.8286	$1,103.83	$1,103.80	$1,103.80