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	$137.94	4.106%	$143.6038	$143.60	$143.60	$143.60
Purchase #2	$116.44	8.294%	$126.0975	$126.10	$126.10	$126.10
Purchase #3	$131.70	9.152%	$143.7532	$143.75	$143.75	$143.80
Purchase #4	$30.83	7.216%	$33.0547	$33.05	$33.05	$33.10
Purchase #5	$82.90	11.357%	$92.315	$92.32	$92.30	$92.30
Purchase #6	$147.81	7.486%	$158.8751	$158.88	$158.90	$158.90
Purchase #7	$34.62	7.549%	$37.2335	$37.23	$37.25	$37.20
7 purchase totals =	$682.24		$734.9328	$734.93	$734.95	$735.00