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	$108.38	4.806%	$113.5887	$113.59	$113.60	$113.60
Purchase #2	$173.91	10.256%	$191.7462	$191.75	$191.75	$191.70
Purchase #3	$84.49	6.616%	$90.0799	$90.08	$90.10	$90.10
Purchase #4	$161.48	6.206%	$171.5014	$171.50	$171.50	$171.50
Purchase #5	$76.31	8.415%	$82.7315	$82.73	$82.75	$82.70
Purchase #6	$190.85	5.257%	$200.883	$200.88	$200.90	$200.90
Purchase #7	$177.61	7.317%	$190.6057	$190.61	$190.60	$190.60
7 purchase totals =	$973.03		$1,041.1364	$1,041.14	$1,041.20	$1,041.10