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	$222.79	8.844%	$242.4935	$242.49	$242.50	$242.50
Purchase #2	$40.31	13.776%	$45.8631	$45.86	$45.85	$45.90
Purchase #3	$151.31	11.242%	$168.3203	$168.32	$168.30	$168.30
Purchase #4	$110.99	11.562%	$123.8227	$123.82	$123.80	$123.80
Purchase #5	$196.97	3.752%	$204.3603	$204.36	$204.35	$204.40
Purchase #6	$32.81	4.320%	$34.2274	$34.23	$34.25	$34.20
Purchase #7	$198.88	3.280%	$205.4033	$205.40	$205.40	$205.40
7 purchase totals =	$954.06		$1,024.4906	$1,024.48	$1,024.45	$1,024.50