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	$234.75	13.408%	$266.2253	$266.23	$266.25	$266.20
Purchase #2	$136.84	3.509%	$141.6417	$141.64	$141.65	$141.60
Purchase #3	$98.45	7.171%	$105.5098	$105.51	$105.50	$105.50
Purchase #4	$67.29	7.412%	$72.2775	$72.28	$72.30	$72.30
Purchase #5	$89.82	13.122%	$101.6062	$101.61	$101.60	$101.60
Purchase #6	$249.48	6.781%	$266.3972	$266.40	$266.40	$266.40
Purchase #7	$212.63	5.115%	$223.506	$223.51	$223.50	$223.50
7 purchase totals =	$1,089.26		$1,177.1637	$1,177.18	$1,177.20	$1,177.10