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	$34.95	11.125%	$38.8382	$38.84	$38.85	$38.80
Purchase #2	$37.80	10.123%	$41.6265	$41.63	$41.65	$41.60
Purchase #3	$42.44	10.783%	$47.0163	$47.02	$47.00	$47.00
Purchase #4	$218.79	3.623%	$226.7168	$226.72	$226.70	$226.70
Purchase #5	$43.98	3.554%	$45.543	$45.54	$45.55	$45.50
Purchase #6	$39.94	8.303%	$43.2562	$43.26	$43.25	$43.30
Purchase #7	$52.81	12.471%	$59.3959	$59.40	$59.40	$59.40
7 purchase totals =	$470.71		$502.3929	$502.41	$502.40	$502.30