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	$58.49	4.688%	$61.232	$61.23	$61.25	$61.20
Purchase #2	$33.28	7.757%	$35.8615	$35.86	$35.85	$35.90
Purchase #3	$90.77	12.561%	$102.1716	$102.17	$102.15	$102.20
Purchase #4	$88.78	3.646%	$92.0169	$92.02	$92.00	$92.00
Purchase #5	$170.72	5.484%	$180.0823	$180.08	$180.10	$180.10
Purchase #6	$206.66	7.153%	$221.4424	$221.44	$221.45	$221.40
Purchase #7	$72.87	12.618%	$82.0647	$82.06	$82.05	$82.10
7 purchase totals =	$721.57		$774.8714	$774.86	$774.85	$774.90