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	$67.66	6.233%	$71.8772	$71.88	$71.90	$71.90
Purchase #2	$87.87	6.437%	$93.5262	$93.53	$93.55	$93.50
Purchase #3	$55.45	11.508%	$61.8312	$61.83	$61.85	$61.80
Purchase #4	$103.99	5.362%	$109.5659	$109.57	$109.55	$109.60
Purchase #5	$204.81	11.757%	$228.8895	$228.89	$228.90	$228.90
Purchase #6	$224.94	11.424%	$250.6371	$250.64	$250.65	$250.60
Purchase #7	$119.66	8.804%	$130.1949	$130.19	$130.20	$130.20
7 purchase totals =	$864.38		$946.5220	$946.53	$946.60	$946.50