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	$232.58	3.837%	$241.5041	$241.50	$241.50	$241.50
Purchase #2	$238.37	6.635%	$254.1858	$254.19	$254.20	$254.20
Purchase #3	$217.85	6.779%	$232.6181	$232.62	$232.60	$232.60
Purchase #4	$38.67	4.151%	$40.2752	$40.28	$40.30	$40.30
Purchase #5	$69.91	11.580%	$78.0056	$78.01	$78.00	$78.00
Purchase #6	$142.26	6.529%	$151.5482	$151.55	$151.55	$151.50
Purchase #7	$127.90	4.544%	$133.7118	$133.71	$133.70	$133.70
7 purchase totals =	$1,067.54		$1,131.8488	$1,131.86	$1,131.85	$1,131.80