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	$217.92	6.160%	$231.3439	$231.34	$231.35	$231.30
Purchase #2	$59.39	7.626%	$63.9191	$63.92	$63.90	$63.90
Purchase #3	$99.31	9.467%	$108.7117	$108.71	$108.70	$108.70
Purchase #4	$82.89	10.418%	$91.5255	$91.53	$91.55	$91.50
Purchase #5	$249.68	8.476%	$270.8429	$270.84	$270.85	$270.80
Purchase #6	$183.81	11.139%	$204.2846	$204.28	$204.30	$204.30
Purchase #7	$87.61	9.460%	$95.8979	$95.90	$95.90	$95.90
7 purchase totals =	$980.61		$1,066.5256	$1,066.52	$1,066.55	$1,066.40