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	$208.65	11.260%	$232.144	$232.14	$232.15	$232.10
Purchase #2	$150.82	11.601%	$168.3166	$168.32	$168.30	$168.30
Purchase #3	$228.73	7.593%	$246.0975	$246.10	$246.10	$246.10
Purchase #4	$149.99	12.567%	$168.8392	$168.84	$168.85	$168.80
Purchase #5	$110.76	11.685%	$123.7023	$123.70	$123.70	$123.70
Purchase #6	$24.40	12.606%	$27.4759	$27.48	$27.50	$27.50
Purchase #7	$45.54	6.690%	$48.5866	$48.59	$48.60	$48.60
7 purchase totals =	$918.89		$1,015.1621	$1,015.17	$1,015.20	$1,015.10