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	$193.45	13.529%	$219.6219	$219.62	$219.60	$219.60
Purchase #2	$41.62	5.337%	$43.8413	$43.84	$43.85	$43.80
Purchase #3	$40.33	12.418%	$45.3382	$45.34	$45.35	$45.30
Purchase #4	$199.43	6.129%	$211.6531	$211.65	$211.65	$211.70
Purchase #5	$49.76	10.230%	$54.8504	$54.85	$54.85	$54.90
Purchase #6	$44.85	11.571%	$50.0396	$50.04	$50.05	$50.00
Purchase #7	$156.35	10.559%	$172.859	$172.86	$172.85	$172.90
7 purchase totals =	$725.79		$798.2035	$798.20	$798.20	$798.20