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	$53.83	3.828%	$55.8906	$55.89	$55.90	$55.90
Purchase #2	$6.64	8.124%	$7.1794	$7.18	$7.20	$7.20
Purchase #3	$176.99	11.243%	$196.889	$196.89	$196.90	$196.90
Purchase #4	$88.96	5.697%	$94.0281	$94.03	$94.05	$94.00
Purchase #5	$17.67	3.109%	$18.2194	$18.22	$18.20	$18.20
Purchase #6	$40.30	7.736%	$43.4176	$43.42	$43.40	$43.40
Purchase #7	$102.32	5.474%	$107.921	$107.92	$107.90	$107.90
7 purchase totals =	$486.71		$523.5451	$523.55	$523.55	$523.50