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	$200.99	5.869%	$212.7861	$212.79	$212.80	$212.80
Purchase #2	$21.78	7.382%	$23.3878	$23.39	$23.40	$23.40
Purchase #3	$30.41	10.265%	$33.5316	$33.53	$33.55	$33.50
Purchase #4	$74.86	4.447%	$78.189	$78.19	$78.20	$78.20
Purchase #5	$175.94	5.392%	$185.4267	$185.43	$185.45	$185.40
Purchase #6	$196.63	13.171%	$222.5281	$222.53	$222.55	$222.50
Purchase #7	$6.60	7.854%	$7.1184	$7.12	$7.10	$7.10
7 purchase totals =	$707.21		$762.9677	$762.98	$763.05	$762.90