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	$199.49	7.613%	$214.6772	$214.68	$214.70	$214.70
Purchase #2	$63.88	11.570%	$71.2709	$71.27	$71.25	$71.30
Purchase #3	$182.75	9.655%	$200.3945	$200.39	$200.40	$200.40
Purchase #4	$108.34	11.479%	$120.7763	$120.78	$120.80	$120.80
Purchase #5	$223.40	3.678%	$231.6167	$231.62	$231.60	$231.60
Purchase #6	$235.57	13.299%	$266.8985	$266.90	$266.90	$266.90
Purchase #7	$112.86	9.440%	$123.514	$123.51	$123.50	$123.50
7 purchase totals =	$1,126.29		$1,229.1481	$1,229.15	$1,229.15	$1,229.20