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	$49.93	9.808%	$54.8271	$54.83	$54.85	$54.80
Purchase #2	$65.46	3.576%	$67.8008	$67.80	$67.80	$67.80
Purchase #3	$178.39	11.260%	$198.4767	$198.48	$198.50	$198.50
Purchase #4	$217.90	4.737%	$228.2219	$228.22	$228.20	$228.20
Purchase #5	$202.90	5.644%	$214.3517	$214.35	$214.35	$214.40
Purchase #6	$102.26	6.248%	$108.6492	$108.65	$108.65	$108.60
Purchase #7	$164.42	12.809%	$185.4806	$185.48	$185.50	$185.50
7 purchase totals =	$981.26		$1,057.8080	$1,057.81	$1,057.85	$1,057.80