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	$190.87	11.650%	$213.1064	$213.11	$213.10	$213.10
Purchase #2	$59.55	7.204%	$63.84	$63.84	$63.85	$63.80
Purchase #3	$106.37	5.272%	$111.9778	$111.98	$112.00	$112.00
Purchase #4	$43.81	4.567%	$45.8108	$45.81	$45.80	$45.80
Purchase #5	$177.63	10.413%	$196.1266	$196.13	$196.15	$196.10
Purchase #6	$176.32	7.387%	$189.3448	$189.34	$189.35	$189.30
Purchase #7	$129.94	5.834%	$137.5207	$137.52	$137.50	$137.50
7 purchase totals =	$884.49		$957.7271	$957.73	$957.75	$957.60