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	$212.82	5.548%	$224.6273	$224.63	$224.65	$224.60
Purchase #2	$163.92	5.246%	$172.5192	$172.52	$172.50	$172.50
Purchase #3	$43.82	3.797%	$45.4838	$45.48	$45.50	$45.50
Purchase #4	$50.29	5.480%	$53.0459	$53.05	$53.05	$53.00
Purchase #5	$180.89	10.817%	$200.4569	$200.46	$200.45	$200.50
Purchase #6	$232.71	4.588%	$243.3867	$243.39	$243.40	$243.40
Purchase #7	$10.33	8.739%	$11.2327	$11.23	$11.25	$11.20
7 purchase totals =	$894.78		$950.7525	$950.76	$950.80	$950.70