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	$134.71	7.585%	$144.9278	$144.93	$144.95	$144.90
Purchase #2	$137.43	10.299%	$151.5839	$151.58	$151.60	$151.60
Purchase #3	$35.96	3.429%	$37.1931	$37.19	$37.20	$37.20
Purchase #4	$247.93	7.719%	$267.0677	$267.07	$267.05	$267.10
Purchase #5	$112.40	11.765%	$125.6239	$125.62	$125.60	$125.60
Purchase #6	$111.27	7.166%	$119.2436	$119.24	$119.25	$119.20
Purchase #7	$200.62	10.601%	$221.8877	$221.89	$221.90	$221.90
7 purchase totals =	$980.32		$1,067.5277	$1,067.52	$1,067.55	$1,067.50