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	$126.38	11.422%	$140.8151	$140.82	$140.80	$140.80
Purchase #2	$19.65	11.421%	$21.8942	$21.89	$21.90	$21.90
Purchase #3	$198.97	8.481%	$215.8446	$215.84	$215.85	$215.80
Purchase #4	$205.78	3.634%	$213.258	$213.26	$213.25	$213.30
Purchase #5	$110.54	9.588%	$121.1386	$121.14	$121.15	$121.10
Purchase #6	$166.97	11.150%	$185.5872	$185.59	$185.60	$185.60
Purchase #7	$174.33	9.191%	$190.3527	$190.35	$190.35	$190.40
7 purchase totals =	$1,002.62		$1,088.8904	$1,088.89	$1,088.90	$1,088.90