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	$202.91	11.160%	$225.5548	$225.55	$225.55	$225.60
Purchase #2	$119.91	11.341%	$133.509	$133.51	$133.50	$133.50
Purchase #3	$187.31	6.446%	$199.384	$199.38	$199.40	$199.40
Purchase #4	$178.40	7.577%	$191.9174	$191.92	$191.90	$191.90
Purchase #5	$92.64	5.818%	$98.0298	$98.03	$98.05	$98.00
Purchase #6	$133.29	6.828%	$142.391	$142.39	$142.40	$142.40
Purchase #7	$150.86	6.467%	$160.6161	$160.62	$160.60	$160.60
7 purchase totals =	$1,065.32		$1,151.4021	$1,151.40	$1,151.40	$1,151.40