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	$68.35	4.816%	$71.6417	$71.64	$71.65	$71.60
Purchase #2	$37.62	7.183%	$40.3222	$40.32	$40.30	$40.30
Purchase #3	$129.27	13.625%	$146.883	$146.88	$146.90	$146.90
Purchase #4	$74.67	8.312%	$80.8766	$80.88	$80.90	$80.90
Purchase #5	$174.46	7.743%	$187.9684	$187.97	$187.95	$188.00
Purchase #6	$233.50	12.134%	$261.8329	$261.83	$261.85	$261.80
Purchase #7	$29.40	5.366%	$30.9776	$30.98	$31.00	$31.00
7 purchase totals =	$747.27		$820.5024	$820.50	$820.55	$820.50