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	$205.38	6.649%	$219.0357	$219.04	$219.05	$219.00
Purchase #2	$42.96	5.842%	$45.4697	$45.47	$45.45	$45.50
Purchase #3	$37.93	12.280%	$42.5878	$42.59	$42.60	$42.60
Purchase #4	$152.48	3.580%	$157.9388	$157.94	$157.95	$157.90
Purchase #5	$192.55	12.805%	$217.206	$217.21	$217.20	$217.20
Purchase #6	$59.76	13.590%	$67.8814	$67.88	$67.90	$67.90
Purchase #7	$245.40	10.411%	$270.9486	$270.95	$270.95	$270.90
7 purchase totals =	$936.46		$1,021.0680	$1,021.08	$1,021.10	$1,021.00