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	$22.90	12.866%	$25.8463	$25.85	$25.85	$25.80
Purchase #2	$124.75	9.320%	$136.3767	$136.38	$136.40	$136.40
Purchase #3	$242.85	4.428%	$253.6034	$253.60	$253.60	$253.60
Purchase #4	$100.50	4.817%	$105.3411	$105.34	$105.35	$105.30
Purchase #5	$185.93	10.867%	$206.135	$206.14	$206.15	$206.10
Purchase #6	$105.71	8.430%	$114.6214	$114.62	$114.60	$114.60
Purchase #7	$194.78	3.111%	$200.8396	$200.84	$200.85	$200.80
7 purchase totals =	$977.42		$1,042.7635	$1,042.77	$1,042.80	$1,042.60