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	$242.58	9.819%	$266.3989	$266.40	$266.40	$266.40
Purchase #2	$237.59	3.288%	$245.402	$245.40	$245.40	$245.40
Purchase #3	$173.98	9.242%	$190.0592	$190.06	$190.05	$190.10
Purchase #4	$40.50	11.796%	$45.2774	$45.28	$45.30	$45.30
Purchase #5	$35.79	11.217%	$39.8046	$39.80	$39.80	$39.80
Purchase #6	$210.90	7.320%	$226.3379	$226.34	$226.35	$226.30
Purchase #7	$40.35	4.767%	$42.2735	$42.27	$42.25	$42.30
7 purchase totals =	$981.69		$1,055.5535	$1,055.55	$1,055.55	$1,055.60