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	$155.62	13.261%	$176.2568	$176.26	$176.25	$176.30
Purchase #2	$5.44	13.360%	$6.1668	$6.17	$6.15	$6.20
Purchase #3	$35.56	12.648%	$40.0576	$40.06	$40.05	$40.10
Purchase #4	$226.78	5.321%	$238.847	$238.85	$238.85	$238.80
Purchase #5	$32.72	13.535%	$37.1487	$37.15	$37.15	$37.10
Purchase #6	$106.34	11.107%	$118.1512	$118.15	$118.15	$118.20
Purchase #7	$187.37	5.814%	$198.2637	$198.26	$198.25	$198.30
7 purchase totals =	$749.83		$814.8918	$814.90	$814.85	$815.00