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	$42.54	5.725%	$44.9754	$44.98	$45.00	$45.00
Purchase #2	$63.96	13.184%	$72.3925	$72.39	$72.40	$72.40
Purchase #3	$244.98	10.399%	$270.4555	$270.46	$270.45	$270.50
Purchase #4	$208.33	5.398%	$219.5757	$219.58	$219.60	$219.60
Purchase #5	$118.33	5.680%	$125.0511	$125.05	$125.05	$125.10
Purchase #6	$177.95	5.109%	$187.0415	$187.04	$187.05	$187.00
Purchase #7	$87.40	9.644%	$95.8289	$95.83	$95.85	$95.80
7 purchase totals =	$943.49		$1,015.3206	$1,015.33	$1,015.40	$1,015.40