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	$137.75	9.861%	$151.3335	$151.33	$151.35	$151.30
Purchase #2	$106.57	8.193%	$115.3013	$115.30	$115.30	$115.30
Purchase #3	$16.99	6.484%	$18.0916	$18.09	$18.10	$18.10
Purchase #4	$100.63	3.807%	$104.461	$104.46	$104.45	$104.50
Purchase #5	$89.75	13.181%	$101.5799	$101.58	$101.60	$101.60
Purchase #6	$46.92	12.526%	$52.7972	$52.80	$52.80	$52.80
Purchase #7	$110.90	11.711%	$123.8875	$123.89	$123.90	$123.90
7 purchase totals =	$609.51		$667.4520	$667.45	$667.50	$667.50