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	$125.70	7.443%	$135.0559	$135.06	$135.05	$135.10
Purchase #2	$117.82	8.196%	$127.4765	$127.48	$127.50	$127.50
Purchase #3	$113.83	4.330%	$118.7588	$118.76	$118.75	$118.80
Purchase #4	$226.98	13.275%	$257.1116	$257.11	$257.10	$257.10
Purchase #5	$198.90	11.560%	$221.8928	$221.89	$221.90	$221.90
Purchase #6	$179.32	3.290%	$185.2196	$185.22	$185.20	$185.20
Purchase #7	$39.82	10.870%	$44.1484	$44.15	$44.15	$44.10
7 purchase totals =	$1,002.37		$1,089.6636	$1,089.67	$1,089.65	$1,089.70