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	$100.70	9.125%	$109.8889	$109.89	$109.90	$109.90
Purchase #2	$84.65	4.647%	$88.5837	$88.58	$88.60	$88.60
Purchase #3	$181.57	3.582%	$188.0738	$188.07	$188.05	$188.10
Purchase #4	$240.88	6.542%	$256.6384	$256.64	$256.65	$256.60
Purchase #5	$140.30	5.420%	$147.9043	$147.90	$147.90	$147.90
Purchase #6	$154.81	12.719%	$174.5003	$174.50	$174.50	$174.50
Purchase #7	$172.93	10.741%	$191.5044	$191.50	$191.50	$191.50
7 purchase totals =	$1,075.84		$1,157.0938	$1,157.08	$1,157.10	$1,157.10