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	$211.64	5.314%	$222.8865	$222.89	$222.90	$222.90
Purchase #2	$139.70	4.275%	$145.6722	$145.67	$145.65	$145.70
Purchase #3	$132.96	7.158%	$142.4773	$142.48	$142.50	$142.50
Purchase #4	$91.71	9.466%	$100.3913	$100.39	$100.40	$100.40
Purchase #5	$204.81	11.381%	$228.1194	$228.12	$228.10	$228.10
Purchase #6	$95.83	6.476%	$102.036	$102.04	$102.05	$102.00
Purchase #7	$157.41	9.212%	$171.9106	$171.91	$171.90	$171.90
7 purchase totals =	$1,034.06		$1,113.4933	$1,113.50	$1,113.50	$1,113.50