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	$181.38	10.314%	$200.0875	$200.09	$200.10	$200.10
Purchase #2	$145.96	7.800%	$157.3449	$157.34	$157.35	$157.30
Purchase #3	$222.53	13.352%	$252.2422	$252.24	$252.25	$252.20
Purchase #4	$6.32	3.193%	$6.5218	$6.52	$6.50	$6.50
Purchase #5	$148.34	7.722%	$159.7948	$159.79	$159.80	$159.80
Purchase #6	$159.43	3.247%	$164.6067	$164.61	$164.60	$164.60
Purchase #7	$154.91	3.212%	$159.8857	$159.89	$159.90	$159.90
7 purchase totals =	$1,018.87		$1,100.4836	$1,100.48	$1,100.50	$1,100.40