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	$208.88	7.351%	$224.2348	$224.23	$224.25	$224.20
Purchase #2	$132.79	8.383%	$143.9218	$143.92	$143.90	$143.90
Purchase #3	$65.59	9.403%	$71.7574	$71.76	$71.75	$71.80
Purchase #4	$71.98	13.579%	$81.7542	$81.75	$81.75	$81.80
Purchase #5	$168.77	13.489%	$191.5354	$191.54	$191.55	$191.50
Purchase #6	$158.48	13.591%	$180.019	$180.02	$180.00	$180.00
Purchase #7	$154.37	12.232%	$173.2525	$173.25	$173.25	$173.30
7 purchase totals =	$960.86		$1,066.4751	$1,066.47	$1,066.45	$1,066.50