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	$143.26	5.744%	$151.4889	$151.49	$151.50	$151.50
Purchase #2	$49.96	3.567%	$51.7421	$51.74	$51.75	$51.70
Purchase #3	$54.82	3.252%	$56.6027	$56.60	$56.60	$56.60
Purchase #4	$78.45	5.204%	$82.5325	$82.53	$82.55	$82.50
Purchase #5	$31.97	6.186%	$33.9477	$33.95	$33.95	$33.90
Purchase #6	$168.31	10.733%	$186.3747	$186.37	$186.35	$186.40
Purchase #7	$221.78	3.774%	$230.15	$230.15	$230.15	$230.20
7 purchase totals =	$748.55		$792.8386	$792.83	$792.85	$792.80