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	$238.93	10.694%	$264.4812	$264.48	$264.50	$264.50
Purchase #2	$88.71	6.673%	$94.6296	$94.63	$94.65	$94.60
Purchase #3	$237.90	5.415%	$250.7823	$250.78	$250.80	$250.80
Purchase #4	$185.64	10.763%	$205.6204	$205.62	$205.60	$205.60
Purchase #5	$156.86	4.710%	$164.2481	$164.25	$164.25	$164.20
Purchase #6	$213.42	12.198%	$239.453	$239.45	$239.45	$239.50
Purchase #7	$137.41	3.543%	$142.2784	$142.28	$142.30	$142.30
7 purchase totals =	$1,258.87		$1,361.4930	$1,361.49	$1,361.55	$1,361.50