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	$142.78	10.608%	$157.9261	$157.93	$157.95	$157.90
Purchase #2	$171.29	4.663%	$179.2773	$179.28	$179.30	$179.30
Purchase #3	$5.54	8.532%	$6.0127	$6.01	$6.00	$6.00
Purchase #4	$250.72	11.341%	$279.1542	$279.15	$279.15	$279.20
Purchase #5	$40.37	11.700%	$45.0933	$45.09	$45.10	$45.10
Purchase #6	$54.36	8.571%	$59.0192	$59.02	$59.00	$59.00
Purchase #7	$67.27	8.767%	$73.1676	$73.17	$73.15	$73.20
7 purchase totals =	$732.33		$799.6504	$799.65	$799.65	$799.70