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	$153.65	9.512%	$168.2652	$168.27	$168.25	$168.30
Purchase #2	$137.34	7.214%	$147.2477	$147.25	$147.25	$147.20
Purchase #3	$79.60	13.702%	$90.5068	$90.51	$90.50	$90.50
Purchase #4	$224.43	7.645%	$241.5877	$241.59	$241.60	$241.60
Purchase #5	$241.82	3.812%	$251.0382	$251.04	$251.05	$251.00
Purchase #6	$110.42	9.460%	$120.8657	$120.87	$120.85	$120.90
Purchase #7	$209.26	6.240%	$222.3178	$222.32	$222.30	$222.30
7 purchase totals =	$1,156.52		$1,241.8291	$1,241.85	$1,241.80	$1,241.80