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	$111.88	13.851%	$127.3765	$127.38	$127.40	$127.40
Purchase #2	$36.69	9.258%	$40.0868	$40.09	$40.10	$40.10
Purchase #3	$86.76	4.266%	$90.4612	$90.46	$90.45	$90.50
Purchase #4	$184.98	4.645%	$193.5723	$193.57	$193.55	$193.60
Purchase #5	$206.35	7.519%	$221.8655	$221.87	$221.85	$221.90
Purchase #6	$146.37	8.390%	$158.6504	$158.65	$158.65	$158.70
Purchase #7	$201.28	5.151%	$211.6479	$211.65	$211.65	$211.60
7 purchase totals =	$974.31		$1,043.6606	$1,043.67	$1,043.65	$1,043.80