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	$89.55	13.412%	$101.5604	$101.56	$101.55	$101.60
Purchase #2	$128.73	9.128%	$140.4805	$140.48	$140.50	$140.50
Purchase #3	$242.93	9.108%	$265.0561	$265.06	$265.05	$265.10
Purchase #4	$196.69	8.232%	$212.8815	$212.88	$212.90	$212.90
Purchase #5	$211.94	5.519%	$223.637	$223.64	$223.65	$223.60
Purchase #6	$76.28	13.353%	$86.4657	$86.47	$86.45	$86.50
Purchase #7	$206.52	12.313%	$231.9488	$231.95	$231.95	$231.90
7 purchase totals =	$1,152.64		$1,262.0300	$1,262.04	$1,262.05	$1,262.10