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	$212.65	11.151%	$236.3626	$236.36	$236.35	$236.40
Purchase #2	$167.29	13.324%	$189.5797	$189.58	$189.60	$189.60
Purchase #3	$132.40	7.279%	$142.0374	$142.04	$142.05	$142.00
Purchase #4	$27.89	12.677%	$31.4256	$31.43	$31.45	$31.40
Purchase #5	$119.96	6.552%	$127.8198	$127.82	$127.80	$127.80
Purchase #6	$43.71	9.427%	$47.8305	$47.83	$47.85	$47.80
Purchase #7	$219.60	7.315%	$235.6637	$235.66	$235.65	$235.70
7 purchase totals =	$923.50		$1,010.7193	$1,010.72	$1,010.75	$1,010.70