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	$127.86	11.491%	$142.5524	$142.55	$142.55	$142.60
Purchase #2	$67.34	8.228%	$72.8807	$72.88	$72.90	$72.90
Purchase #3	$61.93	12.740%	$69.8199	$69.82	$69.80	$69.80
Purchase #4	$226.62	3.453%	$234.4452	$234.45	$234.45	$234.40
Purchase #5	$105.98	8.465%	$114.9512	$114.95	$114.95	$115.00
Purchase #6	$102.27	3.365%	$105.7114	$105.71	$105.70	$105.70
Purchase #7	$65.84	8.461%	$71.4107	$71.41	$71.40	$71.40
7 purchase totals =	$757.84		$811.7715	$811.77	$811.75	$811.80