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	$238.42	5.299%	$251.0539	$251.05	$251.05	$251.10
Purchase #2	$145.54	5.840%	$154.0395	$154.04	$154.05	$154.00
Purchase #3	$250.56	6.182%	$266.0496	$266.05	$266.05	$266.00
Purchase #4	$155.83	11.550%	$173.8284	$173.83	$173.85	$173.80
Purchase #5	$43.25	3.803%	$44.8948	$44.89	$44.90	$44.90
Purchase #6	$7.28	3.599%	$7.542	$7.54	$7.55	$7.50
Purchase #7	$102.84	9.755%	$112.872	$112.87	$112.85	$112.90
7 purchase totals =	$943.72		$1,010.2802	$1,010.27	$1,010.30	$1,010.20