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	$119.89	3.330%	$123.8823	$123.88	$123.90	$123.90
Purchase #2	$43.33	7.140%	$46.4238	$46.42	$46.40	$46.40
Purchase #3	$175.97	6.524%	$187.4503	$187.45	$187.45	$187.50
Purchase #4	$130.66	8.698%	$142.0248	$142.02	$142.00	$142.00
Purchase #5	$50.81	11.314%	$56.5586	$56.56	$56.55	$56.60
Purchase #6	$184.83	6.394%	$196.648	$196.65	$196.65	$196.60
Purchase #7	$142.98	8.658%	$155.3592	$155.36	$155.35	$155.40
7 purchase totals =	$848.47		$908.3470	$908.34	$908.30	$908.40