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	$33.42	11.439%	$37.2429	$37.24	$37.25	$37.20
Purchase #2	$27.28	5.478%	$28.7744	$28.77	$28.75	$28.80
Purchase #3	$41.47	5.648%	$43.8122	$43.81	$43.80	$43.80
Purchase #4	$20.47	4.347%	$21.3598	$21.36	$21.35	$21.40
Purchase #5	$114.89	11.193%	$127.7496	$127.75	$127.75	$127.70
Purchase #6	$69.53	5.527%	$73.3729	$73.37	$73.35	$73.40
Purchase #7	$210.81	6.140%	$223.7537	$223.75	$223.75	$223.80
7 purchase totals =	$517.87		$556.0655	$556.05	$556.00	$556.10