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	$210.42	6.584%	$224.2741	$224.27	$224.25	$224.30
Purchase #2	$105.30	7.195%	$112.8763	$112.88	$112.90	$112.90
Purchase #3	$43.37	5.502%	$45.7562	$45.76	$45.75	$45.80
Purchase #4	$150.95	13.394%	$171.1682	$171.17	$171.15	$171.20
Purchase #5	$158.98	8.223%	$172.0529	$172.05	$172.05	$172.10
Purchase #6	$92.61	3.264%	$95.6328	$95.63	$95.65	$95.60
Purchase #7	$9.90	8.696%	$10.7609	$10.76	$10.75	$10.80
7 purchase totals =	$771.53		$832.5214	$832.52	$832.50	$832.70