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	$58.46	5.123%	$61.4549	$61.45	$61.45	$61.50
Purchase #2	$115.58	10.310%	$127.4963	$127.50	$127.50	$127.50
Purchase #3	$172.71	13.709%	$196.3868	$196.39	$196.40	$196.40
Purchase #4	$164.70	8.284%	$178.3437	$178.34	$178.35	$178.30
Purchase #5	$29.98	4.349%	$31.2838	$31.28	$31.30	$31.30
Purchase #6	$112.32	10.520%	$124.1361	$124.14	$124.15	$124.10
Purchase #7	$94.35	11.156%	$104.8757	$104.88	$104.90	$104.90
7 purchase totals =	$748.10		$823.9773	$823.98	$824.05	$824.00